Summary

I found that the current x carriage and gregs wade in the single plate wouldn't fit so I created an adapter to join the two together.

Instructions

You'll need some pretty m3 long bolts to join the pieces together. Also something to note is that the Nema17 I have is about 40mm deep so if you have something deeper you're going to need a bigger adapter, I'd probably go for a different design in that case - one that can lift the motor clear of the x-carriage itself.

It's designed to be asymmetrical so that the x-carriage had a decent center-of-gravity with the motor fitted, also it means you only need 3 bolts instead of four.

I printed adapter1 but found the nut trap was very tight, I've created adapter2 with a larger nut trap but not needed to print it.

Prusa i3 x carriage adapter