Where you sail you've got a 15kts average which is not bad, and on that fact alone I would recommend a board around 120 l or smaller. But not for you.
Since you are learning how to use footstraps and plane, you'll need a bigger board, I'd say around 150-160 litres for your 90kg. It will give you stability on all points of sail and during tacking/gybing. No point in getting too small, wobbly board for a beginner. You are right that it will be damaged during harness practice, expect catapults, so I think your best bet is GO with an eva deck. Once you master it, maybe you'll want to change it (as opposed to a Futura which would be the keeper maybe), but it's too early to plan your quiver long term.
Edit: what gear have you sailed before?
Last edited by Screamer; 12th November 2009 at 04:47 AM.