I bought a few of these myself, and had some of the same questions that you did. Let me know what you find out. Charlie Dobbins has some points on modifying the pin for these somewhat to make them a little more "smoother" when the secondary goes off, so I made those adjustments to them. I'm anxious to try some experimenting with them on the water line myself. I thought in shallow water they may be a good option for me for rats where a feedbed set would work but couldn't set a #110 and didn't have enough water to drown on a #1. Might help keep a coon foot away from the trap, too. Again, let me know what you find out on them.
Jim-NE