Prusa i3 Y-axis carriage for 4 bearings

When using stainless steel y axis rods and the standard prusa y axis carriage with Igus RJZM bearings, I was having some twisting and binding issues, causing failed homing/failed prints.

I decided to try a 4 bearing carriage to relieve the drag imbalance between the two sides and stop the twisting/binding.

This fixed all the problems and now prints silently with zero twist and bind. Static and dynamic friction have increased slightly vs a 3 bearing or LM8UU solution, but doesn't affect pr