Each state has it's own laws on trailers with reguards to min. weights for brakes, weights per axle, etc. Here is a short list that I edited (direct link) and posted on the Heartland web for our out of state customers.
http://www.heartlandmarinefl.com/Trailer/brake.html
Having had both a dual (leaf axle, yuck) and now a single torsion (much better handling) plus my past experance in both the Coast Guard and in the private sector... If (big if) you can get away with a single axle it is much easier to piviot the boat down the ramp if the runs are short with a single axle trailer
That though may not always possible with a 210.
Enjoy!