Will this ruin the transparent canopies

If you are going to thin future i would suggest using windex. Windex will not craze canopy plastic.

Thanks VanceCrozier

I will try without using the Rubbing Alcohol

I don't think the alcohol would do anything, it should evaporate before doing any damage. I guess I'd have to ask why you're cutting the Future? It airbrushes well right out of the bottle, and will self-level on its own. (I think the alcohol could actually speed this up & may not level as well.)