The use of laminations and extra swivels and shock springs will Indeed cut down on foot damage. Strong springs that lock up the trap will reduce foot movement. I'm not sold on 4 coiling but strong springs are very Important. I also belive Inside lamination will reduce foot damage more so then outside lamination.Both would be better.
Then there Is the animal itself. Some critters will fight a trap with more tenacity then the next one. Sometimes this Is do to a stormy night,or maybe the animal Is being harassed buy something while caught.There Is nothing we as trappers can do to remedy this situation.
I find very little damage on the feet of coyotes and red fox,bobcats seem to never show any foot damage. But the small fragile footed grey fox can really mess up a foot. But then again you can catch 10 In a row with no damage and the next one will be messed up. In my opinion It's just the nature of the beast when it comes to grey fox.