I don't know if this the right way or not, but it works pretty good so far. I weigh 155 pounds and have bounced around pretty good on her.
I used the leading arm off one of those kiddie trailer bikes and doubled up the dropout.
Took out the bearings out of the original wheel and replaced them by adding (welding) a larger bearing on the outside of the non drive side and dremeled out enough to press the other bearing in on the freewheel. Used a 3/4 inch threaded rod for the new axle, welded that to the dropout and Whalah!
It was all trial and error, I fought with it coming loose until I welded the nut onto the dropout and then it was fine. Good Luck, hope this helped and keep us posted on your single sided adventure!!!