I've flown it with the Saito 72, YS 63 and TT54. The Saito and YS dearly love a 13/6 APC. With the YS and Saito put the battery pack over the wing and as far back as you can get it. Put the reciever over the wing in front of the battery. This should get the CG at about 4 1/4 to 4 1/2. For the first flights you might want the CG further forward. Mines now at 5 but I first flew it at 3 5/8. Flew fine but was kind of trickless.