I never really liked Gitzo-styled tripods, but needed an indoor tripod as my homemade one has spiked feet and is usually dirty. The twist legs locks on Gitzos are bad enough, but the center column on some models is especially egregious. I didn’t realize this at the time I bought a used one off Ebay, but it’s impossible to tighten the center lock down enough to keep the column from spinning, or at least it is on the version I have. Markins has (or used to have) a hub retrofit to replace the the yoke entirely, but decided I would try to modify it before spending an extra $180 on a tripod I wasn’t wild about to begin with.
Note the proximity of the lock collar to the platform in the stock image above. If a large format camera is used on the tripod without a head, it becomes really difficult to tighten down the column enough to keep it from spinning. Even when using a tilt head to collar doesn’t seem to lock down securely. Of course you could just pin the column to keep it from spinning, but the tripod feels more stable without the lock collar extending above the hub.
This was pretty easy to do with just a drill, hacksaw and file in a few minutes. Remove the column and locking collar. Cut off the threaded throat flush with the hub and clean up with a file. Reinsert the column into the hub and mark the length to the bottom of the hum, remove and cut with hacksaw. Enlarge the slot in the hub to accept a Chicago screw/ sex bolt, then reinsert the column and drill through to be able to insert the screw and lock column in place to keep it from spinning. Install camera or tripod head.