Here some close up shots of the two center poles I have, showing the
lip that the hub rests on. Notice the two different locations of the support.
In fact, if the lip were placed even higher on the sleeve, the bottom part of the
center pole can be shorter and the top piece longer.
The lip of the sleeve is placed so that the center/middle of the hub is at the height as determined when you calculated the tent dimensions. (For example, my tent was designed with the spokes to be 7 ft off the ground, so the center of my hub sits at 7 ft when the hub is on the sleeve lip. )
The hub must have something to rest on, and the small lip welded all the way around the pole sleeve provides a perfect support. This lip doesn't need to be bigger than about 1/4 inch, unless you really have a hard time cutting the hole in the hub. If so, and your hole is larger and/or sloppy, you may want a 1/2 inch lip |