Contact printer using Space Bag

I had a fun time watching videos on youtube on exposing photopolymer plates. Thank goodness there are industrious folks out there willing to share a tip! I found an interesting one that uses space bags to get a nice vacuum seal. No kidding! Here's the link. For my first attempt at a contact printer I'm going use the space bag method but instead of a cloth napkin like they do in the video, I'm going to use a piece of plywood that has been painted black--just to reduce reflection (I don't know what I'm doing, but I read that somewhere and it makes sense). In the video mentioned above, they use a halogen lamp as the light source, but I'm going full sun, baby! I was just out there gardening and it was too hot to continue, which reminded me I need to work on this anyway and use that hot sun to my advantage. Hopefully my next post will show my contraption and my beginner's luck results (knock on wood). My Printmaking in the Sun book suggests I use a certain brand of solar plates. Oi vey. I didn't think about there being multiple brands with varying exposure times. I've been praying for rain for weeks now, but I have to say I'm hoping for full sun just a little longer.