Hi all,
I haven't done a great deal of testing yet but I can give you some insight on dynamic and constant weight.
I ordered a medium stiffness, size 44, 30 degree angle freediving fin.
First off, build quality is superb. I'm used to the standard russian-style "made by uni student in the back shed" type fin which is excellent performance-wise but is quite ordinary to look at. My last Hyperfin was glued and posted before the glue had dried so some of the wing had separated by the time it had arrived. The Kershkov before this looked reasonable but the Rocketfin looks quite slick.
The wings are much thinner than the other hyperfins i've seen - the rubber is denser as it's not bouyant rubber so it looks a bit "sharper" if that makes sense. The shape is a little different to the Hyperfin, the blade is wider at the base (the foot end).
Bouyancy - the fin is slightly positive, enough so the back heel straps just sit out of the water so almost neutral. Based on some dynamic laps i'm not sure if I like this, my previous two fins were positive which encourages a better glide. Constant weight felt a bit different too, I probably just need to get used to it, particularly the last 15m of ascent where I had to kick a little more to become positive again.
Footpockets - tight, stiff, but not too bad. My footsize is approx EUR 43-44 and I asked for a 44. Foot goes in easily enough compared to other fins and i've been able to keep it on for about 20min in the pool and about 40min in the lake (i've always had about twice as much tolerance in ocean/lake diving than the pool). One of my feet is slightly larger than the other (can't recall which right now), in the pool when I kick I actually feel the pressure on my right foot at the base of my toes which makes me think my right foot is larger. This pressure is quite uncomfortable and the right foot seems to be bearing too much of the downforce of my kick in dynamic. In CWT, I don't notice it.
I think you have to be fairly true to your shoe size when ordering - if you order too big (eg if you're a 43 shoe and you order 46 fin) then yes, it will be more roomy but I suspect the heel strap will be a little loose and your foot will move around in the pocket. Yes, it'll hurt a bit but as you wear it more this will get better. Probably a size bigger than your shoe size would work best. Hyperfin pockets typically curve down to make room for the toes but interestingly Rocketfins do not. Does not seem to impact the overall comfort (relative comfort anyway) much.
Stiffness -
Dynamic: feels too stiff. I've got photos of me kicking a med/soft Hyperfin and putting the blade at a 90deg angle, no such issue here. I need to experiment with kicking style a little as i'm not feeling the love just yet, though this is not uncommon for me with a new fin.
Constant Weight: Oh baby.. Rocketfin is an apt name. This thing flies down to depth and more importantly, back up again. The issues with stiffness I had in the pool do not seem to be there in the depth. I took the fin below 50m on Monday in 1:40 with no noticeable leg fatigue - granted I have been doing a bit of leg work in the gym lately but I could imagine a fit diver with a medium blade wouldn't have much issue finning back from much deeper. A med/soft might be a good option though if you're thinking 3 digit depths though, so to comment on Eric Fattah's post I think that's a wise choice of fin stiffness for the dives you are doing.
Service - can't fault the guys. Prompt responses, plenty of options and discussion and good turnaround time.
Overall comment - a superb looking fin that i'm sure i'll adapt to over time. Seems to be particularly good for Constant Weight, i'll let you know how I get on with dynamic.
Cheers,
Ben