Parts all accounted for, inventory reviewed, instructions reviewed, weekend blocked off - check, check, check and check! 15 minutes into building my RailCore II 300 ZLT I discovered that I clearly didn't know enough about how to tap a threaded hole in metal and brought my plans to a halt.

M3x0.5 tap... broken off inside of 1515 aluminum stock

A new, not the cheapest money can buy, taping set is on its way as well as the needed lubricant for tapping and more 1515 aluminum extrusion. Here's to hoping the second time is a charm!