Modifying SKS Race Blade Long for solid axle hubs
If you enlarged the hole on those, there's really not going to be much material left. I'd worry about it getting mashed to nothing under the nuts.

The other thing is that the knurled surface and generous dropout contact area on track nuts do a lot to keep the back wheel in place. Messing with that seems bad.

I would use either p-clamps or, if possible, an appropriately sized random plastic bracket.