Case trimming...
Dubious--You asked about the Lee Zip Trim gadget, and that question has not been answered. I have one and it works well for me. Also got the Universal Shell Holder for it. Found both @ a gun show for less than retail.
For the occasional times I use the Zip Trim, I just clamp it to my bench. Works like gangbusters.
I use 'em with the Lee Case Trimmer for the cartridge in question. The ball handle cutter is MUCH easier on your hand!
Standard Wisdom is that straight-wall pistol cases don't need trimming, but I trimmed all my target .357 Magnum cases, simply so that the crimp would be more uniform on the wadcutter bullets. Probably unnecessary, but I feel better about the ammo that way, and anything which helps confidence in competition is a Good Thing.
The Lee Case Trimmer only trims to one length, but that standardizes your cases, and the set length of the trimmer tends to be toward the Trim-to length in my manuals, so it works for me. If you want the cases trimmed shorter, take a diamond hone--carefully--to the pin of the length gauge of the trimmer until it is shortened to your desire. (But then obviously you are stuck with that shorter length!)
With neck-sizing my rifle cases, they don't usually tend to lengthen, but I occasionally check to make sure. And of course free range pick-ups need to be checked, and trimmed as needed.
Bottom line: For occasional use, my Lee Zip Trim works very well for me, and I recommend it. You want the Ball Handle Cutter. You want the Universal Case Holder. Both of these make the Zip Trim work even better.