Jeff, thanks yet again for contributing. I think this thread has deviated a wee bit from what I hoped was my main point which is the nose digging in and impeded progress. When I moved the pin one hole out the prop did cavitate when giving it beans. That didn't happen prior to moving the pin.
From what you describe Jeff I think I'm back to where we kicked off, and I have been reading the gauge wrong, which would give me a keel about 60% of max pressure.
Regarding planing, I am quite frankly staggered it planed effortlessly with 5 up and if I had the trim right we'd have planed 7 up without too much drama. Admittedly at full throttle but I'm not expecting miracles and when I bought it I didn't expect it to plan so easily. the previous owner told me his 14 stone son had wakeboarded behind it and I didn't really believe that. I'm thinking its possible now.
I'm putting my money on keel pressure. I'll get out in it again this weekend and have a play.