I don't know much about this but wouldn't it just be simpler to get a slightly smaller propellor?
I've got 3 inch wheels on my LT-40 and that appears to work fine don't go beyond that. Besides the looks being a bit rediculous with such large wheels the weight would be way too much for a trainer.

But I would still go with getting a smaller propellor and keeping the wheels you got.

Just my 2-cents