Only issues I'm still having are the plane seems a tiny bit tail heavy, and I've made my right thrust a little too extreme, which gives it a bias towards the right side and doesn't let me roll to the left, just banks. That's all build slop though and nothing to do with design, and with all that, and doing loops and rolls, the plane has not entered a critical stall once. You should be able to achieve desired CG just from using the 2205 motor, and I'll try that size on my next build some time down the road.
Our science was good
. You suggested that because of the tail plane and wing being one piece/short coupled together the tail plane was acting like part of the wing. This was instantly bad news to me from my experiments with compound delta shapes. I also remembered some discussions with
@Dr. Looping Looie about tailed deltas. The main fix was putting some fuselage length in between the tail plane and wing. That said, I figured the strong vortices created by the delta wing could still interfere. The extra precautions were going with the relatively unswept tail plane, and the two-stage system of winglets to dampen the vortices at the wing tips, and twin tails to fence off any remaining turbulence from interfering with the tail plane. All of these extra measures seem to have payed off.
I have a couple errands to run, but I'll start getting the measurements ready.