First I want to say THANK YOU for posting this as I used this last year when I was just starting to get into this new found hobby.
I just wanted to provide an update to this particular step.
I prepared my books again this year for PHXCC and followed all of these steps again. However, the CGC rep informed me at the show that if you were to follow Step 8 above and submit your comics with that flap covering the cut out Mylar where the signature was placed, your books will be significantly delayed on getting graded. He told me that when they get these books, they just place them to the side as it stops their existing workflow process of bar coding all books when they process them because they have to remove the comic and insert it into another Mylar that has no cutout. He suggested that you ship to your facilitator another Mylar bag where they then can remove the comic from the cut one and place into a good bag. He told me the reason they don't process your books with a cut window in the bag because in the past they have accidentally placed their bar code sticker on the actual book over the signature! So don't do this if you want your comics graded promptly.