My Stiletto was a dense, high wing loading delta, and I agree with Piotrsko on this. It flew like absolute garbage at low throttle, but was remarkably stable once you got some airspeed. The last and most successful test flight demonstrated that the plane essentially didn't fly at anything less than half to two thirds throttle. Granted, it was a lot easier to push a simple prototype test bed than a more finished one like this. As for the yaw slip, it looks like there's not much leverage from the stabilizers to the point of rotation, so that might have something to do with it. I'm no expert in any of this, to be clear. I just messed around with design stuff until it worked, and I know that at least my deltas always needed a lot more vertical stabilization than you might expect.