Kent,

For stable flight, place your CG so that you have a decent
margin of stability. If the dihedral angle is something you're
willing to adjust, increasing the dihedral will give a bit more
stability in the roll axis, but that would not be very consistent
with the type of flight the Cap is intended for, I would think.
For slow flight, make sure that you have a low wing loading.
Within reason, the shape of the leading and trailing edges don't
have much effect on speed or stability.

banktoturn