If you have MB550, those are fantastic if you adjust the pan tension. They say some come with a 5 lbs pan tension and for me that is too high. I have used the MB550 on a limited basis for cat and fisher and they are great.
When I used to run a lot of traps on the ground for big dollar fisher I choose a good #1.75 most of the time, set up on a drag. If you are running a lot of steel and running hard you may want to staple them Thorpe style or stake them. The video shows a stapled trap. Never had a fisher go far on a drag set up but I typically added a wood clog to the chain too.
As my buddy ebsurveyor says, the 1.5 coil is good. I have another good friend that talks about and writes about using the #2 Sleepy Creek long spring.
I have a slug of them too. The double long spring beds really well in loamy woods soil.
If your sets are exclusively fisher, you can guide the hard.
As ebsurveyor said, pre-bait. Pre-baiting works really well on some animals and fisher is one of them.
Use fresh meat for pre-baiting and sets. Fisher are hoggish, use a lot of bait. You will hear and read of some guys only using lure. Do not be one of them.
If I do use skunk, it is not at the set proper where I will end up rubbing my coat sleeve in it, the LDC will be up in the air and close to the set.
Always make two sets at a minimum. It is no fun to have something plugging up a trap when a fisher comes through.
It is no fun to catch a rabbit and see on snow where a fisher had dinner.
These are hard lessons and ones I took when fisher were worth big money.
You can make woods sets that will take whatever comes along or you can target fisher in mostly uncovered traps as suggested. It is really hard for me to leave an uncovered trap, even though they work. I choose to at least break the outline of the trap so I can sleep better. LOL
Good luck and have fun.