rowdog,
When I had my os 160 twin in mine, i had the glow battery right on the cg, and the reciever battery about under the dash panel. I have full retracts, with retractable tail wheel and air ram mounted in servo position. I still had to add 2 full lbs of tire weights to firewall. Came out just short of 25 lbs. Flew well, but engine was tired, and no take-off power. After snap on take-off, and wing replacements, I converted to electric power. Now weighs 21.5 lbs, AUW. Still carry 8 oz of tire weights on motor mount, just behind motor. Battery tray could have been more forward mounted, if I had known how at the time. (This was my first electric conversion. Have learned a lot since.)

The wings carry the weight fine, just have to keep the speed up, even when landing, as she will tip stall easier as weight goes up. If yours flies well now, the dead weight is not hurting. Especially if yours is as light as you mention. When you go with the retracts, balancing the tailwheel assy will require the most weight. If you go with it, that is.