The Flow's are a very supportive binding, but they don't offer much if any highback rotation.  Personally, I feel this is a solution seeking a problem because if you ride with any significant degree of binding angles (+15 or more) the highback rotation available on most bindings isn't really enough.  It's personal preference, but worth considering.  Most every high-end stiff binding is expensive, so looking for closeouts and older models can save you some money.  I was able to get a pair last year's Union Atlas FC for $399 just last month, so be diligent.  Other bindings to consider are the Ride A-10's, Nitro Carver+ , Rome Cleaver and Flux CV's and XV's.  

@deuxdiesel If they don't offer any highback rotation, how do you feel any response during heel side turns? Correct me if I'm wrong but aren't you supposed to "sit" towards the side (drop your hip perpendicular to the edge of the board?). Wouldn't that cause the side of your calf to press against the highback?

Or are you supposed to lean straight back against the highback?

The Flux CV offer A LOT of highback rotation, and the high heelcup is great for clearance and response.  But if they're going on a stiffer carving board, definitely go for the CV LTD with the carbon chassis.  The regular plastic in the CV flexes quite a bit.  I liked the CV on my Freecarver 6000, and have them on the Korua trenchdigger now for some fun, surfier carving.  The LTD go on my Stranda Shorty and JJA C4.

I'm a huge fan of the Cleaver as well (preferably with the Bataleon Infinity strap).  It has a medium-sized disk that provides a bit of mobility/flex, but when can put the pivot mount up it really raises the ankle strap height for more support and response.  The highback is quite stiff and doesn't totally rotate out of the way at steeper angles though.  I actually prefer the highback on the Bataleon Astro FW (and the straps), but you don't get the carbon footbed that really does make a difference.  I use these on all-mountain/freeride boards with 21 degs on the front foot.  I have thought about trying them on the C4 though, just for a little more toe-side leverage.

I'm always shopping end of season deals.  There generally isn't a lot of stock on these expensive bindings, but if they don't sell out you can definitely save a fair bit.

Posted by: @skoonk

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@deuxdiesel If they don't offer any highback rotation, how do you feel any response during heel side turns? Correct me if I'm wrong but aren't you supposed to "sit" towards the side (drop your hip perpendicular to the edge of the board?). Wouldn't that cause the side of your calf to press against the highback?

Or are you supposed to lean straight back against the highback?

Good question- the highback is one part of the equation, but so is boot stiffness, strap location and stiffness, baseplate and disc stiffness and so on.  I have been riding C10's the past two seasons with the highback rotated as much as possible with good results, but at 33/21 stance, it feels a little lacking on deep heelside carves.  I just completed 2 days on my new Union Atlas FC's, which offer zero rotation, and was blown away by how much more supportive they are.  Using the goofy yet oh so fashionable toe cap straps over the top of the boot gives a ton of leverage for heelside turns as well.  It seems to me that a binding like the Jones Apollo that has a bit of a wing on the highback might help, but those wings are biased towards the inside, not the outside.  Maybe they could be swapped around?  Now that the FC's are my new go-to bindings, I might add a third strap and wing to my C10's just for fun.  

As far as heelside turn initiation, it can be done by "sitting" if you have very low angles or ride duck, stretching your heelside love handle/pinching the toeside one, lifting the toes, twisting the board, tucking the back knee/opening the front plus a few other ways, but the best is the combination that works for you- there is no one "right way".  Some are more efficient, some are more subtle. 

Posted by: @deuxdiesel

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It seems to me that a binding like the Jones Apollo that has a bit of a wing on the highback might help, but those wings are biased towards the inside, not the outside.  Maybe they could be swapped around? 

As the owner of a pair of Jones Mercury... The wings on the highbacks are biased towards/curved around the outside actually. So in double posi stances you get good support from the front binding, but poorer support from the back binding. The bindings are clearly designed with only duck stances in mind with the extra support being on the outside

However, I'm planning on swapping my right (back) highback for a left (front) one (I ride regular), thus riding with two left highbacks. I know "justaride" Lars runs with two "front" highbacks for this very reason.

I can snap some photos in a few days when I get home to show how the highback curves around because the photos online don't really show this. I think Lars has a good video showing it off when he explains why he likes the Yes/Now/Jones bindings.

Good to know, thanks!

As promised, top down photos of Jones Mercury mounted at 33/15 on a 164 Stranda Shorty

I actually bought the Mercury for an all-mountain board, but with my 260's the medium had to be adjusted forward and it put the footbed over the edge (even with some shorter Now footbeds).  I tried them on a wider pow board, but didn't like the lack of lateral flex when I wanted to get a little more surfy.  Now they live on my 6000, which is probably the most comfortable combo I've ever had for hard/frozen conditions.  The skatetech feels really cushy underfoot and the biax 6000 is kinda soft, along with the ash topsheet for dampening.

I thought about buying another set of highbacks to swap the rear, but they have enough rotational flex that it doesn't bother me (and highbacks often do bother me). 

The 6000 is fairly short and turns quick, so I'm not really shifting my weight fore/aft all that much, but I do still feel a bit constrained at times.  The skate tech definitely directs your power/weighting.

My medial/lateral rocking seems to have bent them a bit, as the bushings no longer sit flat:

The higher heel cup is great for clearance AND leverage on the heelside.  I felt the toe was kinda lacking, but the Burton Hammock straps swap right on and they're great!  I really ought to do something about the toe straps, they never stay on very well.