I've had US 40's since they first came out.

I've had four US-40's and all of them usually had Saito 56 or 50 engines. I did use Saito 72's and 82's for a short while on one of them. These engines will all interchange on the same mount.

I changed all of them to use a Great Planes engine mount as with a four stroke engine and the original aluminum mount, they are very nose heavy and need a lot of weight in the tail. I also used Dave Brown 3 1/2" treaded wheels to fly off grass. I never had any trouble with the gear breaking loose out of the fuselage.

Two had four servo wings and one of those was converted back to two servos. I presently only have the remaining four servo version. It is the later style red one with the counter balanced rudder. I don't get any thrill from using the crow method of landing approach therefore the flaps are set up parallel with one reversed servo. The ailerons will not raise in spoiler fashion.

They have used Futaba 3004 and Hitec 425 servos and had several hundred flights.

However, if you are going to run the high and low rates as listed in the manual, these servos have marginal resolution at center when using the low rates.

If you want to be a true true 3D person (and I don't consider the US 40 to be the best 3D plane in the world), you should consider the cheaper digital servos.