Okay, I haven't called U-Trip in about 13 or 14 years, and I only call ASA. However, their rulebook is available online at the following address:
http://www.usssa.com/sports/home.asp?Sport=17
Go to the bottom, and you'll see the link to download their rulebook.
The top of page 13 (Rule 2-2-B) says...
The knob portion must be welded, or mechanically attached to the bat.
Sounds like USSSA's intent is that the knob must be permanently fixed, and those bat stinger knobs are out. Personally, I couldn't agree more.