RE: Need Opinions On Engines..
#1. I firmly believe that Unbalanced it correct. You should not test or demo the plane with a larger engine than advertised. I think it will limit your sales since the regular guy, and buyer, will think it has to be overpowered to be able to fly well.
#2. I think your engine size limits need to be revised. I don't think any 1.08's are being made any more. The 2-stroke size should be uprated to 1.20. Then I would test with the OS 1.20. I would also test with the 1.20 4-stroke.