IMHO you would be better paying a little more for a fiberglass canopy Something like these.
http://www.xheli.com/aica.htmlCheaper than most and unlike plastic canopys they will take paint a lot better and you will find your paint work will not crack as easy as it will on a plastic canopy.
A simple test for your friend is to try painting a soda bottle like a pepsi or coke bottleand see if he can get a finish that will not crack and fall off. A lot of the plastics we use today is resistant to any chemical bonding. Good for recycling but bad for us who enjoy airbrushing.
The other idea would be to try making a split plug from one of your existing canopys and then vacume for a split canopy from a thin acrlyic. If you was carefull you would have a nearly invisible seam and you could make an endless supply of canopys. I havn't tried forming 1 yet but may have to try tomorrow and see how it goes.
Would be nice to have clear conopys that can be painted inside so as not to damage paint work but still be able to resist impact
Hope this helps
Darrel