Initial thoughts on my custom masks from Spreadshirt which arrived this week.
The material and printing is very good quality, it's a sort of porous white spongy material with small holes in.
Because of the bunching and creasing, parts of the text get hidden. I'm not sure if there is a solution to this. If you make the text larger, it will encounter more creases; if you make it smaller, each crease will cover a larger proportion of the text.
The masks are quite large — if you put the top part over your nose and stretch them out vertically, the halfway point is about level with your chin (so "BBC", "FEAR", and "AS THE MEDIA" actually appear under my chin). However you can fold down the top seam and bring the whole thing up an inch or so.
If anyone else is thinking of making a custom design, it might be better to keep the design on the top half of the mask so it appears over your nose and mouth, rather than on your chin. Perhaps if you make the design slightly smaller and centered horizontally, it won't get bunched up so much and will be more visible.