nu2rc,

If you have some building experience, you have an option that I and others have used modify! It is not hard at all to mount an OS 12 car engine on the LMH.
There is a concern on the rotor speed, but, that is with-in ones own hands to control (max engine RPMs).

I and others have posted info on this site on doing the conversion.

I fly larger Helios and the LMH is by far the easiest to maintian. Also, the amount of fuel consumed is far less than with larger engines.