Metalguy,
I had this discussion some time ago on here about Greener crossbolts that don't touch the inside of the hole in the rib extension. My feeling is that the crossbolt is mostly a sales gimmic to sell you on the idea that these are stronger than other actions. The fact is that most of the ones I have checked don't touch at all and for the crossbolt to do any good in a catistrophic event, the underlugs would have to stretch before the crossbolt even came into contact with the hole in the rib extension.
The two underlugs have a lot more steel in them and much more area of contact that the crossbolt would ever have, even if it fitted tightly to start with. We had all kind of agreed that the crossbolt was kind of like an insurance policy, you hope you never need to depend on it, but if you do, you're glad you have it there to add extra strength. Personally I think it is mostly a sales gimmick, But, I have several guns with crossbolts on them.
If your gun has two threaded pin caps, you may find that your gun uses a straight untapered hingepin. You then have to go up to the next standard straight hingepin. The problem with that is that I have not been able to find anyone who sells the straight untapered hingepin blanks. All Brownells carry are tapered. Maybe you could have someone with a lathe turn you a new oversized pin. Good luck on your project. Bob H.