I am running a .47 GMS, .61 GMS, .76 GMS and a Tower Hobbies .75. The TH .75 and the GMS .47 are ABC and the .61 GMS and .76 GMS have a Dykes ring. What I have found differance between the .76 GMS and TH .75 is that the TH has a slight bit more power than the GMS on the same fuel (5%) and prop sizing 13x6 (about 300 rpm diff). All are great running engines. I also run a ST G90 on 5% and it is also a fantastic motor. It took a while to get her dialed in but she is purring sweet now also.

Curt