Love your designs. Only issue I'm having with this one is that even the short AlExtruderFront version puts my E3D v6 out of reach of my print bed. I'm using a non-Printrbot stiff Z-axis coupler, which I believe is taller than what Printrbot offers now, so my Y-axis motor runs into the coupler before my E3D hits the print bed.
I'm not opposed to ordering the rigid Z coupler from Printrbot (http://printrbot.com/shop/rigid-z-coupler/) if it fixes this issue. Can anyone confirm whether or not there is room for the rigid coupler from Printrbot with this design? That would need to be my stopgap measure until I can reprint Jon's printable frame (the edges curled on me too much last time, so the part was a no go).