RE: GSP hellcat????????
I used standard servos on every surface including the HITEC 523HBs. I do use a 6 volt pack that gives them approx 60oz but that's not needed, just what I had. I used Pull Pull on thrudder to hide the unsightly horn provided and used two smaller horns under the level of the stab, out of sight. easy mod looks and works much better. The 150 should be awesome, i've seen several fly on a Saito 120 and that is plenty of power.
FYI, I had a small crack form on the top of the turtle deck where the two halves of the glass fuse come together. this is cuased by twisting on the fuse from engine torque and vibration. I fixed this easily with some 4 OZ glass tape and epoxy in the inside. I would recomend you do this before you complete the model especially with a 150 hauling it around!!!
Have fun.