It's easy to match the radius of the hinge pin when recutting the welded hook, through use of an end mill ground to size. I've done quite a few Foxes using this technique along with Ithacas and even a SAC which was challenging because it had a tapered hinge pin.
Bushveld, most of my 'smithing posts on the Fox site are on the private Members Forum and they won't come up using the search function for anyone who isn't an annual/life member and has access enabled. The latest post I did on this is dated 2/7/12 and it's there in the Fox Members Forum along with descriptive text but the pics are missing due a problem with Photobucket.
Here are two salvaged pics showing a Fox hook after welding, and after the hook was recut to within 1-2 thou overlength, and before the spot & fit to the frame. Weld was done by a welding tech and is 100% with no dark spots/voids showing after the machining. Also, note how little "heat" propagated onto the hook. Frank Silvers