I do this regularly and find it worthwhile. I secure the wheels to the ground, and I use stretch all wrap around the fuse opening, starting from the front going toward tail, this allow any overlap to prevent seepage through the layers, two wraps is usually all it takes. This allows you to see inside fuse with engine running and watch the servos move, etc. When done unwrap and toss into garbage (Other advice - get the original roll back to kitchen before the wife notices).

I've never tried a trainer races, sounds like fun.