With all due respect, you're essentially asking us the question, "What's the right way to do the wrong thing?"

That engine is too big for that plane. It's just that simple. If you want to minimize the oil mess go with a 4 stroke glow engine around .60 size. If the issue is that you're using a covering material that won't stand up to glow fuel, you just need to change your plans and do something fun with one of the film coverings or do a painted covering job with a glow fuel proof paint. I truly do understand the appeal of having gasser airplanes, but there is a practical minimum limit where they just stop working well.