Oh, Yeah! It's a CONSTANT problem........
You're quite correct, the bushings inside the base swell. Only solution is to takea rasp file to them. Don't quoge them out too far - if you do, then the pedestal wobble.
Switching to a different type of base is a costly proposiiton.
A few years ago, I remebered seeing some inserts that would convert these bases to the 3/4" pin type..... I had seen them at both Wally World and in the BPS catalog - but they were no longer there. So I called Swivl-ease, the company that makes the bases....... The lady (and I use the term loosely) there told me they had them in stock; no one sold them so they were all returned. She said she would send them to me at $15 each plus shipping........ Whoa! $15 each? Distessed merchandise to fix a fault in YOUR bases and you're gonna charge me 15 buxs each? That's more than the $9 they sold for at the stores! I've already gone out and purchased 2 new Swivl-ease seat poles and seat mounts as it is! Now you're gonna charge me an outrageous amount to fix a problem in the design of your bases?....... "We're the only ones who have them!" she replied.
Now you all know what I think of the people at Swivl-ease.
me