I don't think the gap in the film fork will cause you issues, though I had an opposite problem once with my Sears KS-2 (re-branded Ricoh XR-7).
The plastic top of the rewind had broken, and a local camera chain "fixed" it along with "fixing" a sticking shutter and "fixing" a light leak. (None were fixed, I had to do it all myself.)
Anyway, the replacement plastic, and shaft, were wrong. The plastic top was close, but a bit thicker, holding everything higher than it should have been. Basically, this caused the shaft of the fork to be slightly too short. When rewinding, it would slip quietly, making me think the film was all the way in the canister. Ruined some photos that way. Oddly, this only happened with Kodak canisters, not Fuji - go figure.
I finally found the correct part and replaced it (I have acquired about 20 compatible cameras for parts). I did as suggested, using cloth to prevent marring of the shaft while I held it and unscrewed the top part. It was very easy, and I now have absolutely no problems.
Again, I don't think this will be an issue for you, as the fork is longer, not shorter, when you adjust it. So long as it's not too long for the cartridges, you should be fine. If the gap bothers you, you can find some small washers, or cut/file the shaft (be careful to not mess up the threads), or find a spare fork/rewind assembly of the right dimensions.