Screen shots (version 0.5):

Double skin sled

Single skin sled with LE tube

A different view of just the ribs and LE tube.

The top skin is built using a different skin factory, the TE of the skin is split into larger sections. This is less accurate, but could be easier to sew. You could also imagine doubling the number of rib's using this skin factory would greatly increase the accuracy of the leading edge (where most of the power is generated) while leaving the trailing edge easy to sew.

The rib dialog box.

The canopy shape dialog (showing LE shape and TE shape)