I once caught a fox in a pocket rigged with a drowning cable. I expected to catch either mink or coon. Part of the fox was floating. From a distance I thought I had caught someone's dog.

I agree with "Boco", Whether using footholds or body grip traps, the main things to remember about the boxes are to set on LOCATION where mink travel, camouflage the box well with surrounding vegetation/snow or whatever and HIDE the BAIT with dry grass so the mink will enter the box searching for it, and keep the bait fresh.

I have also caught a number of fox in 120 mink box sets over the years.

I've had both bobcats and coyotes reach their front feet into marten boxes and get caught by the foot. In all cases they pulled out of standard Victor 120's.
I'm pretty sure that if those 120's were Belisle 120's, and if they were fastened better I would have held them.

Another one from a couple seasons back.

I got a few coyotes in Belisle 220 sizes traps and they were all held by there front leg. One by the head. I bet a 120 Belisle would hold one like Waggler says.

None of those are in magnum traps,all mink traps(old waxed bmi 120s).
Those traps also kill otter stone dead,they dont even get their head out of the box.Otter carotids must be near the surface since they expire so quickly in those small weak traps.
The only time i ever remember catching a canine by the foot in a bodygrip was a silver fox, that leaped up to a marten box set opening up five feet off the ground.Probably caught a dozen or so fox by the head in mink boxes over the years.
Most of my marten traps are b 120 LDLs
Caught a cat by the foot in one once that was set on the ground.
Caught a few cats by the head in elevated 120 marten boxes,set with opening down and opening up.

Surprize catches like that each season keeps the job of trapping interesting