The fence size is the same as Timo's, but allows cutting at -45, 45 degree angle.
In addition:
Added .1 mm to fit more easily
Add lock mechanism with 2 M3nS nuts and 2 M3x14 bolt (from the MK3S+ Fasteners spare bag) to lock the track. The bolts push 2 flexible plastic slices to avoid damaging the track.
An opening to be able to insert a clamp.
The drawback is that only vertical printing is possible on the MK3.