I've got the new OS 50 in my US40 and it's a great match. JeffC has the older 50 FSR ABC in his and hovering at 2/3 throttle is cake...with lots of power. A true stump-puller with the 50.

We've got some video of the US40 with the OS 50 (new and FSR ABC). Although Jeff crashed his (video supplied), we dig the plane.

The 46 will work fine; several of the gents at our club use them on the US40...but it doesn't have the bite that a 50 or even a 72 four stroke may have....

http://www.ncsa.uiuc.edu/Cyberia/peo...l/rc_us40.html

-Juhan