Uhmmm If memory serves the OS .32 SX-H is the heli motor. The SX is just the normal aircraft motor.

A throttle pipe is a pipe that will give you good throttle response through the whole rev range. A tuned pipe will most of the time only give you much higher revs but the motor will "climb" onto and off the pipe at a certain throttle position. Which is sometimes a drag on these planes. I have learned to work around it though.

We have proven on the plane I linked down at the bottom that the Irvine .39 out performs the OS .32 quite far. The weight penalty is virtually nothing, if not nothing. Although the West .36 puts out a 1000rpm more than the irvine swinging a Master airscrew 11X4. On my Irvine I get 14900 rpm with the MA 11X4. I don't know about the webra, although the west is a tweaked webra from what I understand.

Here is my comp Fun-Fly which is a South African designed plane. 50inch wingspan and weighes 3lbs.
http://www.spacey.rchomepage.com/images/Shotgun%205000/