Sand it round for absolute sure. Angled leading edge stalls at higher speed compared to rounded. I have seen a discussion of the idea of leaving the 90 degree angled le in the root, and gradually rounding as you go out to the tip, on the theory that this will guarantee root will stall first, not the tip. But my guess is with this model a rounded leading edge all along the span will be a gentle staller with no tip stall problems. If I'm wrong, you can put an angled stall strip along 20% of the root span and fix the problem. Out of fifty sport/scale kits or more I've built, I've never seen plans calling for anything but rounded leading edge. Maybe some jets like a sharp le, but I don't do jets. (Not smart enough or brave enough or rich enough.)