ive flown the tower trainer rtf (training a club member on one) w/ a tower .46 and it is so overpowered its crazy. for basic training purposes we fly around at 1/4 throttle with a 11x5 apc prop, the plane floats along like a trainer should. i see no reason why a .46 engine with a 12x4 or 12.25x3.75 wouldnt fly a .60 trainer well enough to get the person out of trouble if they need too. you would prob only get 50 feet of vertical if u went strait up but at an angle you should be fine.

what i would do is decide what u would rather buy, you could buy the .60 sized plane and if the engine isnt enough buy an engine as well and save the .40 for something else. or just buy the .40 sized plane

if you really want a .60 plane then get the .60 and try the .46