Sevens, good to know! I may rethink purchasing one of these. Of course, I should ask about the degree of effectiveness for those shields. Is it a situation of "it helps a little" or "it does the job"? I ask just because I've seen some members here mention problems with shooting prone. I don't do that often but I like to have my bases covered.
On point 1, I really started thinking about this when I started shooting .460. If you've never done it, you can feel the energy loss as heat over the entire upper surface of your grip. Photos of the blast also show a lot of flame escaping. Take a look at this example I found on Google Images: