Thanks Don, and I have also gotten pretty much the same advice elsewhere to just forget about cutting down my K40 antenna.
A large part of my problem (beyond the 55" length of the K40 whip), is that my CB antenna mount is located up really high on my Hanson tire carrier. Here's a shot from the rear of my TJ that shows this:
As you can see, there's only about a foot of the base of the antenna before it clears my hardtop. Trying to use a tennis ball in that first foot is still going to leave the majority of the small diameter and very flexible stainless steel whip antenna above that point to still flail around (and I am not too keen on trying to otherwise tie the antenna down like some folks do).
By the way, the K40 hitting my top isn't so bad (other than the noise), but when it whips around and hits my side rear windows, it makes me wonder at times if it's going to hit just right one of these days (and with enough force) to finally crack one of them.
Anyway, based on this, it looks to me like I will probably be better served by just replacing my current K40 with a shorter antenna (and I see that there are some K40 Super Flex fiberglass antennas that are as short as 2 to 3 feet long). But I'll have to see how these shorter antennas can interface with my current K40 mount, because one of the things I like about my K40 is the 1/4-turn twist-off/quick-disconnect capability for quickly removing the K40 coil & whip assembly from the rear of my TJ.
Thanks again,
Don