Didn’t like how the rear muguard fitted and I’d drilled the holes for the indicators in the wrong place, so bought a new mudguard (UFO YZ125-250 98-02) and did it again, properly.
I ‘eyeballed’ the cut like last time, but did make note of the cutting dimensions and indicator hole positions so anyone can repeat this with minimal grief. Once cut I held the mudguard in place with tape to get the positions for the side bolts then drilled the holes for the rear light mount.