I binned the idea of a BOV in the end; I decided that a grand for something that's not really required wasn't cost effective.
In my short time on the Revo (57 hours from July through October -- was quite poor weather!) I didn't find the gag strap to be at all of a problem. I can't even think which order I put them on, probably mask last.
When bailing out I grab the bailout reg with my left hand and then switch the DSV lever down and roll the mouthpiece and DSV down with my right hand and out of my mouth, then put the bailout reg around my neck in the normal deco-cylinder way and purge it into my gob and breathe. (I do the purge - not exhale - so I can keep gas in my lung just in case it's fecked up and I need to get back on the loop -- need some breath left to clear the mouthpiece. From experience, I'd once forgotten to turn the stage on!).
Putting it back I can either loosen the gag strap or 'roll' the DSV mouthpiece back in my gob and exhale as I open the DSV.
I'm in my early days with the box and I'm really keen on doing bailouts. Just want that completely automatic so that should I need it, no problems.
From seeing that presentation which sparked this thread I do want to try some gag-strap tests, maybe in a pool (remember them), where I relax and see what actually happens with the loop. There was a picture in that presentation of someone "unconscious" and on their back (simulated) with the loop firmly in place. I've a suspicion that I don't have the gag strap tight enough.
Up to that presentation, I'd never really thought of the *real* need for the gag strap. Yes, it's bleeding obvious when pointed out, but I was more thinking that the point of the gag strap was more about keeping it in place and taking some weight off the loop.