OK, in the composite pic it's obvious to me that the extra wing area of the red model has too small a stab and a shorter tail moment compared to the dayglo lime green model. That alone may be why you need a more forward CG.

I suggest you look up Tail Volume Coefficient for the horixontal tail volume (there's also a vertical tail volume coefficient for the vertical area) and compare those values. I suspect that if you increase the size of the stab on the red model so the TVC matches then it'll fly better.

Your airfoil looks fine BTW. I can see that it's no more radical than many in use these days and should fly well.