Update:

PHYSICAL
PCI-E 1 (x1)   --> 750 TI (1x riser, shorted)
PCI-E 2 (x16) --> 750 TI (16x riser)
PCI-E 3 (x1)   --> EMPTY (shorted)
PCI-E 4 (x1)   --> 750 TI (1x riser, shorted)
PCI-E 5 (x16) --> 750 TI (16x riser)
PCI-E 6 (x1)   --> 750 TI (1x riser, shorted)
PCI-E 7 (x16) --> 750 TI (16x riser)

It's been mining all night.  Not sure if I want to try PCI-E 3... that sort of "what if it don't work after i make a change" mentality.

http://www.neochron.net/mining/six-miners_832x624.jpg