I got it all wired with RAMPS and all the axis calibrated with a digital slide scales. I have about .02 mm backlash in the belts. The cheap 3/8' X 12 acme lead on the Z is not accurate as I hoped but good enough. It varies about .05 mm over a 20mm movement. When I got back home off the road earlier this week, one of Roy's 300X300 Helios heated bed was here waiting on me. Also got the 2mm taper reamer to use on the barrels of the extruders. I'm going to try to get some barrels made today and mount the heatbed and see how well the extruder work.
I'm going to use a 24 volt power supply on the bed and the rest will run on 12 volts.
Here is the bed setup. I got in on the "Open Rail" kickstarter and on the next one I build, I'll use the rail on some 20x80 for more stability on the bed.
And Roy's Helios bed
Rodney