I'm of the opinion that Bill did do a double crossdraw. A lot of the photos we have available were definitely staged as hell - this one is a classic example:
There ain't no way he carried with either a big bare blade like that or with his guns "fluffed out" - all of which is clearly for visual effect. Remember, getting your picture taken was a really big deal, a "high tech and new thing" that people dressed up for. You also had to stand there for a while for the slow as hell exposures.
I carry an SA daily in a crossdraw setup of my own design that allows major adjustments to both ride height and tilt angle. This is my favorite setting, which is pretty similar to how Bill carried (but only one gun of course):
This setup is very "high and tight", more or less similar to how Bill carried.
Because of the adjustments available I've tried (briefly) a more "conventional" lower-and-more-horizontal setup:
I can also change the tilt angle around completely and set it up for lower strongside carry:
If you're curious about how this holster works, go here:
http://www.thehighroad.us/showthread.php?t=418769
Back on topic: there's a way to draw from the same side as the gun with butt-forward carry, but it ALWAYS leads to sweeping your own body. It's called the "Prairie Twist Draw". A good pic is available at:
http://www.willghormley-maker.com/AdvantagesOfCrossDraw.html
This will get you tossed out of any match and most ranges. I *do* practice it some, with an unloaded gun ONLY, because if my right hand is tied up, shot up or broke I may have to get to it off-handed.
But it's not my standard draw at all and I don't think it was Bill's.