SKYRAIDER: CG and fabric

Hello all - my first post. I am resuming construction on my Skyraider I; at the point of wiring, rigging, and covering. Engine will be an 4a084 4-cylinder, 4 stroke military surplus "General Military Engine". I assume many on this forum are familiar with it. But here is my question: With the heavier engine, I want to get a good estimate of the CG before covering. That way I'll know whether to mount the battery aft at the tail, and other considerations. Can any builder tell me how much weight placed where on the fuselage will reasonably duplicate the CG contribution of fabric and finish? Thanks!

Jim