jeraldman, I'm prob an 'intermediate' with my main sailing being bump/jump & flatwater blasting. My main board is the same volume as my weight, and as long as there is enough wind...it's perfect. I also get on my 135lt board occasionally, but find that I can't stay on the water for as long, and end up sore afterwards.
If you go down to 85-90lts your waterstarts will improve, and too many catapults can be contributed to harness line setup & stance. I found that the smaller board helped me improve my technique. At 110kgs, the smallest board I've had the pleasure of riding was 80lts with a 4.2 sail...was blowing a constant 30kts+ on the Pt Fairy Loch & if we had enough consistent wind around here, that would be my board of choice!