I have Eddie's book, and I've been practicing the stretches for some months now.
If anything has seen the video where he talks about "developing the squeeze" and he hugs around his leg to show it.
Well....I can do full lotus now, but I have a lot of lower body strength.
My legs are tree trunks which could compete with any heavyweight kick boxers, so I can hardly if at all get my arms around one of my legs like that, in that rear naked position.
I have pretty strong grip though, but as a 6'3 200+ pound guy, I don't see why anyone who doesn't set their mind to it couldn't do rubber guard at a REASONABLE sized gut.
Here's a little secret though, come in close...closer......people who let themselves get too big to physically be able to do rubber guard, jj, or any sort of martial art effectively no matter how much time they put into it, probably don't have the will power to do the kind of reps it takes to get it down in the first place.
Though that's just my theory as a recovering fat guy.