I have a 1998 283 Convincor with twin 454's (310hp) deluxe cabin....fridge, sink, long tabs. I was running 23p Mirage plus's and could not keep the front of the boat down in rough water. Always had the tabs down and still bouncing up and down. My boat is very tail heavy with the twins. I bought some Hydromotive QIV's (22p) this year and tried them Friday. I am very pleased with the results so far. I did not go far (had to tow a buddy in) but the boat came up on plane fine, picked up about 2 mph at 3,000rpm and the boat ran nice and flat with no tab in some pretty rough water. I am thrilled so far.
Your buddies boat sounds like the x-dimension is to high if he is blowing out all the time.
Talk to Kipp at the factory. He had a 283 with a procharged single. He could help you out.