So after haunting ebay for a couple months I've managed to grab some pretty good deals on slides. What you see is one each of 3 sets ranging from $60 $80 and $100. I was pretty excited about the 45's, but now that I've been able to hold them and realize just how massive they really are, I'm a bit hesitant. I was going for a lightweight, easily transportable machine capable of sherline mill work but with a larger envelope but the pair of 45's weigh 50 lbs alone! Plus any amount of 80/20 I would mount them to would be dwarfed by the rails.
I was thinking of using a single 45 for one axis of a fixed gantry, however this would impart a large torque that could wear out the ends of the bearing block where the majority of the load would be concentrated. A more traditional knee mill type setup would keep the cutter centered above the block and reduce torque. I'm just not sure yet, as it seems to be somewhat of a waste to mix and match such disproportionately sized components.