The slot on my router table fence is a little over 4 inches from the table but my feather boards are adjustable as I would think all feather boards are to compensate for the thickness of the part being routed. So then if you are installing a T-Track in your fence the important thing would be to make sure it is positioned to allow the feather board to be adjusted. I just looked and the bolt to lock the feather board in place sets about the middle of the feather board slot when flush with the table top. Another thing to consider is, if you need a stop block build your own from a piece of scrap wood and two 1/4-20 hex head or T-Track bolts with wing nuts to lock it in place. Paying 20-30 dollars for a pretty aluminum or whatever stop block is insane when 1 or 2 can be made that work just as well for 2 dollars or less.
-- If it won't fit get a BIGGER hammer.
