Ok, so it looks like we're sorting out the fact that the caps on there now are not what was originally on there.
I went to hardware store last night, looked around for some type of spacer.
Here's what I found:
I purchased a 3/4" length of white nylon(?) tubing from plumbing aisle. The tubing slips over the space left between my post and the post cap, removing the extreme amount of play on the plastic. I've got enough tubing for 1,000 games as you only use a tiny bit!!! Cost about $4.
Not "stock" but just though I'd throw this idea into the mix. You can always dye the tubing also if you are using colored caps, but you don't really see the tubing that much.
So plastic are *supposed* to have some play in them? This helps them absorb impact better without breaking - hmmm, makes sense, although I could see some rubbing on the underside of the plastic as a result unless you put some mylar down on it.