Saito 120 in my Edge 540. Added some balsa triangle blocks to the rear of the firewall for my own personal security. I don't think it really needed them though, it's a well built plane. The 120 provides it with unlimited vertical...as in, it doesn't even slow down going straight up.[X(]

EDIT: I wanted to add the following disclaimer: I think the 120 is overkill for this plane unless you really wanna push it into 3D, which I do not think it is designed for. It builds a bit on the heavy side for a 3D plane of this size. To keep it light and smooth in IMAC style, a Saito 100 or OS91FX would most likely be the better choices. (Call it second thoughts after the fact )