K8200 Y-belt tensioner

K8200 T5 Y-belt has no room for a static tensioner once you have assembled the printer, so here's an idea.
This thing prints without support material and can be mounted
without disassembling the printer.

You'll need :

3 hex socket cap head bolts M4x16
5 hex socket cap head bolts M4x20
7 washers M4x8,8x0,8mm
6 washers M4x20x1,4mm (or slightly bigger)
5 M4 nuts
3 M4 self locking nuts
5 M4 serrated lock washers
3 ball-bearings M4x16x5mm like SKF 634-2Z