I was finally able to test glue a piece this evening. It took me 6 weeks to get to this point, but I'm on schedule for Awesome Con in 8 days.
I roughed up the back of the piece with 220 grit sandpaper to give the Sil-Poxy more "bite". Per the instructions, I coated the piece and the canvas with Sil-Poxy. After two hours, holding perfectly.
Now to figure out how to glue the shoes without making a mess.
Here's the finished product. The costume is really coming together. If I can get to the MakerSpace to finish the bat Tuesday evening, I'll actually be done before the night before the con.