Great setup.
I'd do the same but my 2nd Travelite is still in transit after repairs.
Tomorrow night I have a gig to shoot some couple/family portraits at church. I have plenty of space, but only 1 Travelite 750 and a 580. I'm thinking of:
Key - Travelite with 30"x40" softbox at camera axis, slightly raised above, pointing downwards
BG - 580 bounced with silver umbrella, placed directly behind subjects towards the white seamless
Does that sound okay? I have other mods like beauty dish/shoot-thru umbrella, but I'm thinking this is simple.
Sorry for the hijack, BTW 