It's a wonder they didn't sink a bearing in that hole. Even something like Nylon/Delrin/Teflon would be an easy/inexpensive solution, and simple to replace in the event of any wear over time. BTW, if this ever happens, remember you heard it here first
If I start getting wear in the hole, I would probably be inclined to take it to a machine shop, have the hole bored out slightly larger, and put my own sleeve in there.
I purchased this item last week and have been able to use it a bit on a photo shoot in Montana I've just returned home from.... A little background for reference is that I've owned the original Wimberly and the Mongoose 3.6 with drop arm so I'm quite familiar with gimbal heads. First impression is that it's very well made. I really don't think the hole everyone seems concerned about will be an issue. I used it with my 500mm F4 and 800mm F5.6 and it easily handles the load. Pan is very smooth and overall it seems more stable than the gimbal heads. To me it performs more like a fluid pan head than a gimbal. You can let go of the setup without it flopping. With careful tension adjustments on the ballhead its' quite secure as long as it's relatively level but if you tilt to far forward or back it will flop. Best to tighten the ballhead when moving but I did that with a gimbal as well. My intention was to be able to travel with just one tripod instead of 2.I usually travel with one tripod with a ballhead and one tripod with a gimbal. I think with this product I could do that without any problems.
saving half of the cost!