I think you'd be a much happier jack in a true solo boat than trying to reconfigure a Northwind.  I'm sure it can be done, but wind is going to be more of a problem than you think, even on small lakes.  Your odds of being windbound will go up enormously soloing a tandem rather than paddling a true solo.

However, if you really want to do it...

"Seems like it would fit" won't be good enough if you are going to move a seat.  The seat will need to fit the width of the gunwales very closely wherever you install it in order to not significantly stress the hull.  If yours isn't very close to an exact fit, then you'll need to buy a new seat (not too expensive) and cut it to fit the new location.  

You also likely would need to add thwarts where you remove seats as a seat acts just like a thwart as far as eliminating unnecessary stress from the hull material by helping the boat (and gunwales) to hold the proper shape.  Do you really need to remove the seats for anything other than aesthetic reasons?  If not, I'd just leave them as is.