I'll write more later, but this is a mod to pulsemedia's improved Y carriage, further reducing the crossbar's ability to rotate in Z (it shouldn't).
The top piece can be used alone with stock hardware, Adding the bottom piece will require replacing the 4 M5 axle bolts with M5x50mm bolts (you'll need 8 for both carriages) and a full set of spacers (4x eccentric nuts, which you can print, and washers/nuts to match the other spacer's height on the inside wheel axles). Everything can be printed or picked up at the local hardware store (even in the States).
One word of warning -- the hole positions have been adjusted, so the bottom plates are not compatible with Pulesmedia's top plates -- If you already have his, you'll have to reprint the set.
If you want to print the spacers, I've had good success with these, but metal ones are nicer ;) https://www.thingiverse.com/thing:2628309