I did a thing a while back that worked out real good. I went to yard sales until I found a rig for $10. Sometimes it''s an old Sunfish rig that someone has had up in the rafters of their garage for ten years, other times its a sailboard rig, complete with mast, sail and wishbone.
Fix up a good posthole type mast step, be sure to hang a rudder and tiller, then go get into trouble. When you make it back to shore, come up with a list of fixes. You''ll probably have to make leeboards, a good mainsheet, maybe rig shrouds and a tiller extension, but all this can be cheap and you''ll be sailing.
By the time you get the whole thing sorted out and working good, you''ll know for yourself exactly how big or wide or forward or aft a perfect rig for that boat should be, and you can sell it and get a 16 footer like all boaters do.