I found out something this year about my 31 that may give a little more hp. It turns out that the center cushion on the rear bench seat is velcroed in and there is a hole behind it.

Can you say forced air ...

Not sure if it will make a difference or not, but I used to get more speed on a couple of other boats that I had when I lifted the engine hatch a little. (Not recommended) Never did it with any of my Sonics because the rear bench seat goes up with the engine hatch.

i have this on my 35 too. Did your old 35 have it ??

I never noticed it on the 35. For all I know, maybe all of the Sonics have this and not just the 31's.

I would think that more air is better. Anyone have an opinion if removing this will help with mph?

That is there for when you can't raise the engine hatch. It allows access to the ram bolts so you can raise it manually.
Or in your case put a scoop in there and see what happens.

I'll check this weekend!

not mine!