I have a 5 cell sub-c pack on top of the engine box and it is still a little tail heavy but flyable, just a bit touchy on landings.

I considered the OS 160 also but had to try the new 200 first..Some people say the 160 may need a pump and I didn't want to go there, so hence the 200..With the standard mufflers I would say the 160 has a little more top end power.. Both engines swing the same prop but i think the 200 has better throttle response, it is very fast to spool up...I have not weighed the plane but it's light...I would say 11 to 12 lbs. max...

Jack