RHD,
w/ the UCD the motor is inverted thus on normal motor putting the exhaust on the left side of fuselage, that is if your standing behind it.

If your using a rear exhaust motor, then the UCD has a channel the the front part of fuselage for tuned pipes. My brother has a YS61 and tuned pipe on his. The only thing is that he has to detach the tuned pipe when he takes the wing off. But its not problem.

I saw pictures of the bottom part of fuselage somewhere here on RCU. and that shows the channel in fuselage.