RE: Seagull Gee Bee Z
I would put your Gee Bee on the balancer & then use the battery to find your balance point.
I found with this model there are plenty of locations to mount your battery to achieve your
CG with out having to add dead weight ....& my model was very nose heavy with the 170R3 !!.
you'll probably find yours needs to be forward of the CG mark at a guess , but chuck her on the balancer first & see where you are .
Regards Steff.