6 inch prop probably would have been fine on 3S, but I guess on 4S it lets the magic smoke out. I would think a 5 inch prop on a 2205 should be fine on 4S. Best insurance though, would be to invest in a watt meter, and do some static pulls, and get some real numbers. I have a “Watts Up” meter. I think it was like 30$ on Amazon. I luv it, ands it’s paid for itself by a drastically reducing my magic smoke emissions.