Most open cockpit folders can be configured for tandem or solo. Look for
kayaks from Klepper, Folbot, or Nautrid. Many people paddle solo from
the back seat. I do this myself with my Klepper when I am to lazy to
move the seat. The only problem is the kayaks tend to weathercock (the
wind tends to blow them off coarse easier), unless you weight the front
end. Some people put water bags or coolers in the front seat. I just
correct my coarse more often with my paddle. If you paddle with a
rudder, it shouldn't make a difference unless you encounter a really
strong wind.

Check out http://www.foldingkayaks.org/

Cliff Kotnik wrote:

I'm evaluating tandem kayaks for a purchase this spring. I will
sometimes want to paddle solo.

I'm interested in opinions on whether I should look for a model with an
adjustable seat so that solo operation is from the middle or if solo
paddling from the rear seat is just as good.

Thanks,
Cliff