$32 for a SX delivered great find!

Your right a pusher setup is the easiest and has several advantages. The one down side is the prop is in dirty air and cannot reach it full potential as far as speed. There was only one full sized speed plane built as a pusher, in the aerodynamic forum they really talk it down quite a bit as far as potential for speed applications.
With my setup it balances with the battery back about another inch and a half so most of the battery mass is right on the COG just a bit forward. With the motor I am using the battery has to offset the weight of the electric motor which is lighter than it's glow counterpart.

Still I do like the idea of less fin with the pusher it should really reduce the induced drag considerably and still sounds like an idea worth trying.

Edit to add:
With my Demon using the sheathing as stressed skin pretty much eliminated the need for the forward spar. A a side note my Stingray has no spars, it is all stressed skin construction where the wing is only 3/8 of an inch thick. One of the things Mike Conner and I had talked about was to thin the wing out on the demon even more going out to the tips. That was part of the experiment with building wings 3/8 of an inch thick to start with.