I have the same boat as you and mine does the same thing if you turn it hard. I did ask about it at Samspeed marine (I live in Gloucester) and the engineer there said it is to do with the shape of the hull. He said that it will splash or cavitate and that there isn't really much you can do stop it doing at least one of them. I've tried and I have come to the conclusion he is right. Trimmed out one notch seems to be the best balance I can get. It only cavitates in hard turns or extreme acceleration and splashes at +75% throttle.
Launch and recovery of my SIB I found to be particularly difficult (especially the latter). Eventually I discovered that submerging the trailer to the point where the boat could beach on it (only floating freely towards the engine) then lifting the front of the boat and dragging it to a position where pulling the trailer out would not cause the boat to move in relation to the trailer; was the best way. I had to have some guide posts made to stop the thing moving laterally.
I did have a picture of a recovery but I can't find it. Anyway's about 2/3 of the bunks in the water works for my trailer and you can see the guide posts in the pics
You aren't far away so let me know if you want to see my it in action. I'm no expert btw, has all been trial and error!