I would definitely do gas. Both the Da50 and the DL50 seem to be the engine for this plane. I can only speak from experience on the DA50 but I have absolutely no reason to doubt aerobob as he has never steered me wrong

I can also say the OS160FX works well but not near as well as the 50cc engines. Whaturi and I once flew both "versions" at the same time. He was roughly 2lbs lighter on the OS160 but I smoked him coming out of a hover and he was never able to catch me. What he did not know is I did not come out of the hover at full throttle, I slowly added power on the way up

Even at the weight I am at I still have a hard time with IMAC on this plane, it's setup correctly but it's almost too light. Wind just tosses it around. I could not even imagine what it would be like at 11lbs to 12lbs. I took it to a meet 2 months ago and placed sixth with it in a mild crosswind, didn't take it to the next one in an even worse crosswind and placed second, now this was a Comp-Arf 2.3M Extra 330L, I know I know, I am comparing apples to oranges.

Now, please do not get me wrong, I love mine to death, it owes me absolutely nothing and you could almost say I owe it and is a great lunch time plane but for IMAC you have to be quick on wind correction with the rudder