I've recently put together a tower Koas and its a blast to fly but seems to have some strange flight characteristics. Just for fun I put two aileron servos which I can turn on as flaperons or mix elevator and flaperons. From its initial flight it didn't need much if any trim and flew straight and level. However while it flies straight it appears to fly crabbed to the left. This is most notable in a flight up while making a hammer-head turn. It goes straight up but just sorted crabbed over. The other odd thing is that when I switch the flaps on I can run the flaps full down or full up (spoilers) and the plane still flies level under power. Doesn't pitch up or down. I thought that the switch wasn't working but when I brought her down it definitely was working. On the other hand when I switch on the airbrakes and throttle back the spoiler function seems to work as advertised as I can mush it in for a landing. With regard to the crab my initial thought was that it must have something to do with engine torque but then thought that would exhibit a left hand turn rather than crab (and also it crabs going straight up after I've throttled back.) Also just for fun I have a gyro hooked up to the rudder as we have horrible cross winds sometimes. The crab isn't effected one way or another when the gyro is switch in or out. -steve-