I believe Neil did something very similar.. Maybe he'll be around soon!
Believe it or not, Tom cuts a slot for them in the 84mm scales. I bought a set from him (And subsequently lost the knife a week later in Chicago- but the most glorious week of my life it was...) and they seemed like they'd hold up just fine. How he does it, he will probably never tell, but if it can be done with the even smaller 84mm's, I'm sure you could do it with 91mm's. But I'm with Neil, save yourself a headache and buy some from sosakonline.com for $7.50- really not a bad price at all considering how grateful you will be. I bought some for my Mechanic and I would do it all over again if it was my last $7.50. And back then, it probably was