This is improved version for Athruz great post.
Now u can secure the Y belt holder with zip ties to prevent from the belt to slip.
In my case to get 270 tension on the belt for long term it is a must from the original holder.
There is a great write up by RHDreambox on the Prusa forum. I give him the credit - check it out for even more fixes he did good work on all 3 Axis's. He was a main contributor to this file and thought process.
You might need to use a 12 mm M3 now instead of the 10 mm M3, this mount is a bit thicker so you need a tad bit longer screw.
You also need drill new hole for the 3rd motor screw (this is optional & not a must ).