Sam,
Thanks for the Downey tip. I would never have thought fabric softener would dissolve salt crystals. I have actually two Sea Tec horse collar BCs. One which, I can hear the air leaking out of the inflator so I cannot test the BC for leaks. The elbow on these wings does not unscrew like on a modern wing. The other one does hold air but looses a bit overnight. I don't think it due to a hole but who knows. I have not replaced the rubber on the dumps but will when I rebuild the inflator.
SeaTec made excellent equipment, they were very popular with dive shops in Florida in the late 80s early 90s. A friend gave me his SeaTec BC and I immediately demoted my Beuchat BC to backup duty. Alas, I did sell the SeaTec because it did not fit anymore. If I wanted to go back to a jacket BC, I would look for another Manta.