I don't like to undo the velcro for fear it will wear more quickly and not grip as well. When I first got the Twiddler I adjusted it quite a bit until I finally got it dialed in, and it seemed to be headed that way. Plus, now that I've got the strap how I like it, I wouldn't want to have to undo it and play with it all the time.
Using the unused slot's an interesting idea though. I'll have to think about how that might work.