I also fly the Tower-75 and I used anywhere from a 10x10 on a propjet to a 13x7 or 8 Zinger wood- 12x6 IS small for the 76 sounds like a 61 sized prop there... I dunno what yur flyin' but if you are doing any 3D you might try a 14x4 also-

Keep us posted!
james
P.S. Native San Diegan also--