The last place I'd drill and tap something is on the swing arm of a motorcycle, IMO. Just thought I'd point out that drilling and tapping something that wasn't meant to be drilled and tapped could compromise its structural integrity. Forewarning.
And if that thing comes off while flying down the freeway it will ride the chain back up to the front countersprocket. IMMEDIATELY stopping the bike. I mean IMMEDIATELY as in you flying off the bike and landing 80 feet in front of it! I'd rather take my chances with the rare
chain de-railing which will not halt the bike.
But hey good luck with that!