If you were like me and hopped on the $69 deal last month the document had provisions for two. I don't believe you need two witnesses in WI but it didn't bother me.
I just had two people at the bank sign for me. And when I added a rifle to the Schedule A today while at work I had two co workers sign the additioal Section A as witnesses.
It's probably easier to find witnesses that you may or may not need than to get folks on Arfcom to stop implying that you should have invested $350 into a local attourney so that they could give you legal advice when you have questions like this.
I'm not a lawyer, nor am I providing legal advice. I'm just letting you know what I did with my WI based NFA trust because I don't think it's neccessary to invest in a lawyer for some of these things.