Salmon NFX 16' mounting drill size

[wuttheheeck]

Hey all. First post, long time troll I have a new Salomon NFX. I'm mounting it at my rental shop with the FKS. Can't seem to find a recommended drill bit size and it didn't come with any paperwork. Anyone ever drilled into a pair?

 

[robboadd]

3.6

 

[DrewVG]

3.5 X 9