Another aproach you might want to consider. The Hobie 20 uses nylon drainplugs that simply thread into threaded holes in the sterns, Once I forgot mine and to sail for the weekend I epoxied the holes shut (I know ... ) after I got the boat home I redrilled the holes and taped them to fit. No fittings necessary.

Always borrow money from a pessimist. He won't expect it back.