Designing and building a flying wing RC model from scratch XFLR5

This is my attempt to design and build my own flying wing. I wanted to build a small, portable size wing that would be easy and fun to fly. I used XFLR5 analysis tool to verify my vision (I’m not an expert user). The wing came out very light and also very wobbly. I used packing tape and 3x1mm carbon fiber spars to stiffen it, but it fluttered like crazy at certain AoA. Apart from flutter, the wing flew pretty well. It glided well and it was stable. I could hover it at 50% power. Just what I was trying to a