ST-45 is a good call (I have been meaning to try one of those or the ST-51)... The Morris powerhouse is basically a Rossi-45 [X(] and that would have been fun to watch!
To the gent who is building the uproar and bought the OS-50SX, nice work! I have one (w/Tower muffler $15-) and I could not be more impressed--- It is in the same category as an Irvine-53 IMHO

and that is a raving endorsement for me---
The Webra-50GT is the lightest of the main-stream engines and has TONS of power, for anyone engine shopping please consider the Webra--- and it runs on 0-5%
Also, for the folks using STD servos remember you can use a 6V RX batt. and get from 48 oz. of torque to about 60oz. on a Fut- 148 or 3003- no regulator required...