This setup may help but if your wingloading is really over the top -nothing will help The end dam and even a dam at midpoint a tall one really does work in models this size
the removable sideforce generators (dams too)on the Showtime models demonstrate this very clearly
I clipped the wings on this EDGE and having flown the unclipped version - I liked the clipped one better
subtle but slight improvement - roll faster (shorter span ) and slow speed hung in a bit better