Thank you for pointing that out. That is a strange bolt pattern.
https://www.moto-lita.co.uk/bosses/cobra-barrel-boss-1/
It sorta reminds me of factory stringers and ribs that need replaced due to impact damage or corrosion and the new stringer or rib usually comes with pilot holes. If it does they seldom line up and you have to fabricate the part by hand. Thanks to Random Randy's "drill where I feel like it" technique.
Luckily I have a BDR.