Why use polycarbonate? That is my least favorite plastic to work with. For the pellet stove, why not aluminum? It's easily machined, filed, etc. and colored or coated.
The primary reason is that I don't pay a penny(1) for polycarbonate sheets
I have a friend who sends me free polycarbonate sheets classified as "industrial waste" that has been discarded because of defects, but which I can still fully recover.
Usually if a whole sheet of polycarbonate is 1000x600mm, with thicknesses ranging from 1mm to 5mm. When a solid sheet is discarded, I manage to recover 70% of its area, in the worst case I obtain many small pieces which can still be used to machine small parts.
Many parts of the bicycle are made of aluminium. The brakes, the derailleurs, the wheel rims(3) ... every now and then I file, cut, fix, polish those thing
I find it much more difficult to work with aluminium, both because I would have to wear a closed mask(2), and because I have to anodize, de-anodize (in soda caustic), rather than polishing with a brush using the natural aluminum oxide.
Furthermore, both the drill bits and the files are different. For polycarbonate I use wood tools, which are not suitable for working with aluminium.
(1) in return, I gave my friend about two dozen wheelbarrows of wood, already cut to size for his fireplace
(2) aluminium dust is toxic for the nervous system, but is also harmful to the pulmonary alveoli
(3) lately I've been using (experimenting?) wooden and resin rims, same concept, but better than the one used in the 1940s