I think there would be a couple of issues here related to 40 sized trainers. First, the weight would have to be offset in the rear (as has already been pointed out). This will make your trainer harder to land (more weight = more wing loading = faster landings). This is against the desired traits of a trainer. Secondly, the engine might not fit the mount at all (but, it may!). Thirdly, you couldn't get the ground clearance to fit the sized prop that thing needs to keep from over-reving it. Now, with a computer radio, you could set the travel adjustment, and it would never reach WOT. That might be a solution. However, I would still be scared of the torque that thing would have against the firewall when taking off. You might just rip it in half on the runway! I agree with most--a 60 sized trainer would be much better. I still would change the travel rate so that it would go to WOT, though. Especially at first.
Just my .02