With 5″ Legs, you would have:
Usable Height: 4.5″
Leg Height: 5″ (Usable Height +0.5″)
Z Rail Height: 12″ (Usable Height +7.5″)
Lead Screw: 7.5″ (Usable Height +3″)
EDIT: BTW, when you cut your X/Y rails, just cut all 3 of each to the same length; makes for a decent guide to keep your stepper wires off of the belts.