RE: an Idea for the leading edge
Sharp leading edge is bad !!!
It does not help speed. You want the LE that provides the correct airflow over the airfoil used... that makes the wing work efficently.
Sharp LE = VERY pitch sensitive - the air can not decide which way to go for a very simply visualization.
Please do not confuse the sharp razor edges you may have seen on 1960s era fighter/interceptor aircraft as something related to speed. They were necessay for the supersonic flight environment. But they also caused take off and landing speeds that were WAY up there.
Models (and most aircraft) fly extremely sub-sonic.
The suggestions of others here will help you gain some speed. Get rid of drag where you find it.