I have a Supertigre 91 in mine with slimline pitts muffler. Ground clearance is not a problem with the prop, I think I run a 13-8. I got rid of the plastic turtle deck and used balsa formers balsa sheeting. Most of the time I use 3/4 power, full power on take offs and if you want vertical. I suggest building the version with two ailerons. Mine weighs just a shade of 7 1/2 pounds. Be careful of the balance as you build to avoid excess weight in the tail. I didn't need to add weight, but had to put the battery under the tank to make it balance right.

I first saw this plane fly a number of years ago by an "old timer" who used a Webra 90. A 61 two cycle or 91 4 stroke would probably be fine, I just liked the extra power.