We all want to maximise the range of our equipment, that's understandable. However there is a point when going bigger or smaller simply won't give you anything, just worse handling. I've tried that a lot. A 10m won't damage your board, but try one if you can before buying. For a heavy sailor I'm not sure it's advisable to go to the absolute recommended max. My guess is that 7.5 and about 9.0/9.5 (7.5 and 8.5 a bit too close) would cover all the useful range you could get from your 144 (but again, try and see). Marek is right wrt sail type, 2/3 cam freerace better than full-on race.