For speed, you'll really have to experiment as each boat is different and the same boat is different depending on how much ballast and people you are carrying... generally speaking more weight = more speed. On mine (x-15), it can be great at 10.4 if it is "lightly" weighted or up to almost 12.0 if I have a whole bunch of weight.
One thing I've thought about trying is taking off the swim deck as it seems to be the source of a bunch of the turbulence you mention. I haven't tried it yet, but keep thinking about it. It would be a pain in the *** getting in and out of the boat, obviously. And a pain getting the platform on and off... not very practical for most people and certainly not me (hence why I've never tried it).