RE: FLUTTER problems flying the "U Can Do 3D"
With just about all 3D planes in this size, you need to stay with a 4" pitch prop or less. And every time you descend, throttle to idle.
One of the guys at my field lost the stab on his UCD 46. I recommend you run Kevlar or weed eater (string trimmer) line around the stab tips, fin tip and fuselage bottom. It adds nothing in weight and stiffens up the whole assembly.