I have a pretty small trim tab, maybe 3"x6", with about 25 degrees of deflection in each direction. It's way more than I need for normal flight throughout the weight range, but when the flaps are down, it's not enough to counteract the nose down pitching moment. It doesn't really bother me, and like Jones said, I sometimes fly the thing all day and never touch it, but if my elevator came loose with flaps down, I'd be sunk immediately, rather than having a chance to figure things out if it were trimmed properly in the landing phase. See http://home.hiwaay.net/~langford/trimtab/index.html for more details on it. The MAC trim servo (RC Allen now) really is easy to install, but considering the price, the power window servo that Dan Heath and some other folks have used is attractive if you're on a budget.
Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net
