RE: Questions about modding an Enforcer...
I'll leave the debate as to weather this would make a good speed plane or not to the others. [:'(]
To answer your question about CG, the plane flies fine in the stock configuration, at the stock CG location. The relation of the fuselage length to the wing will not change the CG location appreciably if you lengthen it, but adding canards will. It is essentially adding lifting surface in effect making the wing act as if the chord were longer. If you follow the established mods, follow their CG recommendations. If you roll your own, the CG will have to be re-plotted which is easy to do using the various web based calculators available.