O.k. I think it might work, I just wouldn't use the phrase "I'm sure" without trying it or hearing from someone who had, so I was wondering if you had.
I have a defective ATI stock for the No.4/5 which you can borrow to prove it, if you aren't in a hurry. I can give it to a friend who lives there and visits his sick mother here every few weeks, then you can get in touch with him to pick it up. (I got it second hand without a receipt and I painted it before I installed it, so I can't return it for a refund, but I would want it back because I'm thinking of sending it to ATI partly out of curiousity that they might tell me what they think about how it got like that, and maybe they'll feel sorry for me and send a replacement for good PR.)
On mine the forestock is bent in the vertical plane so it slopes down away from the barrel, but it fits correctly around the action on a No.5 I have, so you could know for sure whether they fit before you buy one. But if you buy one and it doesn't fit, I expect you could sell it for most of what you paid, so maybe it would be worth it to just go buy one.
