I am sure others may be able to help more than me, but I'll give you my horse's feedback.
i originally purchased the dressage suberpanel- and boy it was great. because of body limitations, I've been struggling with riding. i did notice that the suberpanel left some marks on my high-withered tb mare. She didnt really ever object to the saddle, but then again, we only ride every so often. I dont know if under a regular schedule she'd say differently.
This is my theory- the suberpanel was limited and caused problems because of me: the way I sat in it and the way I interferred with it.
Anyhoo, I also have a prolite gp. I just used that for the first time a few weeks ago on this mare. It has a set of shims in it, and a mattes 1/2 pad, prof choice girth. My body, though it struggled the common struggle with the saddle (my lower leg wanting to go backwards and tipping on my fork), was much more comfortable in this one. The mare did not object at all, and no marks were present.
A little story to go with this post:
To set the scene: it has been 2 years since this mare and I had done any real under saddle work.
2 weeks ago a friend and I went to a schooling show. For grins and giggles and also to support my friend, we went to a schooling show and entered the same classes. I figured I'd just bring her for the exposure, and if I got to ride and all was well, that would be a bonus.
Not only did we ride, but we placed in every class, 4 in total. Kind of funny that we were competitive against this group- we got 2nd's and 3rds out of 8-9 students, :lol:
2 of the classes were w/t over ground poles- the mare and i havent really stepped over anything in 2 years, nevermind a mini-test in front of people. :lol: :lol: :lol:
Afterwards the judge came by and congratulated us, and told me my mare was beautiful and looked so happy and calm out there. She also began to give me advice like : changing my saddle to a hunt seat saddle, asking my horse to "round up" blah blah blah. I let her finish and then told her that not only was this my first time riding in this saddle (that requires some getting used to), this was my first time riding this horse for anything longer than 5 minutes in over 2 years! :lol: I also told her that every treed saddle ever tried has elicited a bucking/rearing/speed-going 'fest, and that most of her relaxed nature had to be due to the saddle she was wearing. She quickly changed her tune and said that she was amazed that i literally pulled this horse out of the field and that she did so well, with a brand new saddle and no preparation. With a little consistent work, she should be amazing.
LOL I totally agree

:P
So there ya go. The fhoenix prolite gp was great match for the both of us. I'm sure the suberpanel would suit as well, I just need to get my own act in order and not get in the way of the saddle.