I dont have a problem with drilling, but, I'd probably drill the fender also and bolt it on with a low profile 5mm screw and nut, or maybe even fit a Riv-nut.
Drilling will be easy since there's a dimple and you have the stays to use as steady rests as you punch through the far side.
(OP- See my response about rustproofing in your other thread here)
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