Surfskis vs Kayaks ....

Kemi congratulations on finding a boat that feels great. That is hard to do for many of us. I think the problems you had with the surfskis are not from poor trim, but from the relatively low seat of surfskis. People with stiff back and hamstrings have particular difficulty with that. The fact that you like to sit closer to the pedals and prefer the higher seat of a kayak also suggests problems with flexibility. Sitting close takes strain off the hamstrings. The xt has a very deep bucket and will give that uphill feeling. The boat is not pointing uphill however; it is just your body pointing that direction. As far as making the seatting position more comfortable, many people raise the seat of their ski by adding a foam pad. Also, the trivial weight of the shield on the v12 does not affect the trim of the boat at all. Even a full liter bag of water placed infront of the footplate makes very little difference. I find the epic weedless rudder to be 100% weed free in all conditions, and it gives very little resistance cutting through thick mats of lake weed. It does require the weedless weedguard, rather than the smaller standard weedguard. There should be 5mm or so gap between the guard and the rudder. Anyway, i dont mean to sound critical, i just dont want people to get misled. Glad you found a good fit in the viper 55.

Well said, zachhandler! What you say is basic knowledge to folks who have even a rudimentary understanding of kayak ergonomics and body mechanics - posts like Kemi's (that are full of misinterpretations) can be misleading to someone new to the sport... Unfortunately, some such very basic facts like these could take years to figure out. And I wish there were more adjustment options for skis. I am experiencing some of the same issues as Kemi with respect to my seating position and can confirm you are absolutely right about the seats being low and hamstrings being tight being a bad combo. Although, it might also be a matter of the seat bottom shape disagreeing with the paddler's bottom - in one of my boats I feel the rear of the seat is lower than the front (the actual seat area where my bum is, not relative to the feet). So, while I can sit upright, it requires extra effort to not slouch, even though I don't feel my feet are too high relative to my bum. In some kayaks one could put a back band to help with such lower back support, but the backband interferes with rotation and is generally used mainly to rest against it and to keep you in the seat in rough water and rolling...

@Zachhandler
When I was experimenting with the seat position I also moved the kickboard(also in increments of 7,5mm), so I always had the same distance between seat and kickboard. So I am sitting in the boat with fairly strait legs and feet's glued to the full plate kickboard with a strap. So when I rotate my knees move up and down and I sit completely upright. If there are some small downwind conditions with waves, I don't have to lean over the boat and paddle to catch a wave, but I can keep paddling in my ramrod strait paddling position and the boat just flies. But for all I care I could be doing it all wrong, but for the first time since I learned to paddle a sea kayak, it feels right to me. In a sea kayak you sit in a frog like position(legs) and that makes it easier to get a proper paddle position(in my opinion), so the feeling I was searching for, was the baseline that I had achieved in a sea kayak. Had I not had that baseline, I would have given up a long time ago.
Regarding trim in the V12, I have been playing around with putting some weight(.5-3 Kg) behind the kickboard. When I put weight there, the boat is a bit slower upwind, but it tracks better and it flies over small bumps. If I don't have any weight there, the boat feels more lively/loose and I can feel the up and down when paddling over small bumps. When I had a load of 3 kg and was going upwind, the nose slice through the waves instead of the normal behavior of climbing over them. So in my case I can see and feel a difference.
I did experiment with seat pads in the Fenn Xt, but found it very difficult to get it right. In most cases when I came back from a trip it would hurt like hell, because something was a little bit off, so I gave up on that idea.
About trim in the Fenn XT, when you have to lean so close to you feet that you could kiss them in order to catch a wave, then there is something off. To me that is a clear indication that there is to much weight towards the stern and one should move some weight forward. To paddle that boat was a bit like playing seesaw with someone weighing more then me.