Generally when I build a speed wing I extend the bottom skin foam so that it meets at the trailing edge where on FT plans only the top skin is. (hope that makes sense...
) Also the speed wing doesn't have the cambered FT tips. If the wings are cut already you can always iron the trailing edges and enclose the wing tips after. If you re-enforce the spar you could taper the foam spar so that the wing has a more consistent airfoil as the wing tapers towards the wingtips, essentiall making the wing thinner towards the tips. All of those steps will help out aerodynamics a fair bit.
Check out
@nerdnic speedwing videos, lots of great ideas there.