Nah, I don't think you really need to worry about too much of an offset. Those quilts are wide enough that they will cover the footbox. The ElDorado's footbox is a little more of a radical 'out' than the BB because it has a tie-out line that pulls it out and up without your feet in place. I actually think the BB with no foot tie-out will be an even better fit now that I think about it.
I LOVE an excuse to test something, so I'll hang the BB tomorrow night and use my RMS in UQ mode and report back. I've had my eye on a nice little stealth site close to my place, this gives me a great excuse. Thanks!