It's always been my policy on my Tornado to not use the mainsheet cleat when there is anything more than a few knots of wind. This way, I can release it in an instant to prevent capsize. Another thing to consider if the wind comes up, you might want to try dropping the main entirely and sailing on Jib alone. Tacking will be quite tough, but you should be able to gybe around to the other tack if necessary.
From seeing the Venture cat photos posted earlier, I think it looks alot like a Hobie 16 or 14...in terms of hull shape. Personally, I've never liked these low bouyancy designs...very sensitive to where you place the weight and always seem to have the leeward hull submarining.

Mike.