I did similar, trimming side sections out of a plastic and alloy front guard to fit it through a fork, and eventually it snapped at the place I'd trimmed it (so right underneath the crown). If you can support the front section of it another way, with a stay forward of the fork (mine is now attached to the basket above it it!) or something that might be stronger.
Yes that is what I thought, have a set of stays towards the rear of the fork as usual but add a set of stays towards the front of the fork to support the muguard better an limit flex that might induce cracks where it would have been made slimmer/weaker
I did similar, trimming side sections out of a plastic and alloy front guard to fit it through a fork, and eventually it snapped at the place I'd trimmed it (so right underneath the crown). If you can support the front section of it another way, with a stay forward of the fork (mine is now attached to the basket above it it!) or something that might be stronger.