I hardly ever make an otter specific set.With a limit of 2 to 4,dependent on which part of the state I am trapping.I catch most of my otter in my beaver castor mound sets.
With low limits like we have--I spend more time avoiding catching them--and wisconsin trappers limitations are even greater.
Dam cross overs and pinch points will take your otter.Crossovers from one body of water to another ,also work well. I stick with 330s,I have doubled on otter many times and trippled ,once.
The thing I liked about trapping in Mississippi--no limits on otter, and a very big population.
The otter population has grown greatly in the last decade--Missiouri went from no season-to no limit ,in many parts of the state.Iowa now has a season, and several more states are on the cusp of a season.
Good luck to all.
Tom