Shrink plastic help

[christmasjedi.livejournal.com]

I've been experimenting with shrink plastic lately - specifically Shrinky Dinks - but I'm having quality issues. First of all, black Sharpies don't seem to work well, as the ink comes off during or after baking, so I need to find a new permanent marker to use. But the biggest issue I'm having is that my pieces come out of the oven all pock marked and totally unprofessional looking! It isn't entirely obvious until you catch the light, but then you can see dozens of pits, divots, and imperfections that just look awful.

I'm baking at 325º in a conventional electric oven. My pieces are placed colored side up on brown paper on a cookie sheet. I've been using a magazine or notebook to flatten them as soon as they come out of the oven.

Has anyone here had similar problems and know how to fix them? It's a fun hobby, but I'll have to give it up if I keep getting pieces that aren't worth displaying. Thanks!