Thumb to finger tip in a relatively fixed position is very different than thumb to first and second knuckle in a repetitive motion. Don't take my word for it, try it. If it feels like something you want to do 8 hours at a time then go for it. It seems uncomfortable to me though.
While the idea really intrigued me, I really just wanted to share a cool little website I found with you guys. If I do end up grabbing it, I'll be sure to post a tutorial.