I'd stock whatever sizes are best for what your customers are buying. If, after a time, you find that some sizes are not moving quickly enough, ditch those sizes. Add new sizes when you see a need.
I've made some adjustments since the last time I posted these. Here's my latest (hoping my memory is good):
8x10: clear, non-glare (have to make the non-glares ourselves, none of my suppliers carry them anymore)
11x14: clear, non-glare, conservation clear, conservation non-glare
12x16: clear, non-glare
14x18: clear, non-glare
16x20: clear, non-glare, conservation clear, conservation non-glare, museum
20x24: clear, non-glare, conservation clear, conservation non-glare, museum
22x28: clear, conservation clear
24x36: clear, non-glare, conservation clear, conservation non-glare, museum
32x40: clear, conservation clear, museum
36x48: clear, non-glare, conservation clear, conservation non-glare, museum
40x50: conservation non-glare
40x60: clear, non-glare, conservation clear, conservation non-glare, museum
I used to stock everything in the 22x28 and 32x40 sizes as well, but found the non-glares were not selling well in those sizes so I dropped them. For example, we just sold our last sheet of 32x40 conservation non-glare last week. I had purchased 3 boxes of it back at the end of 2006, and it took that long to sell them. At nearly 2 years per box, there's just no reason to keep that size. I'd rather cut down a 36x48.
I'd stock museum in 11x14 if it were available.
