Nearly all the bicycle seat post QR units with an aluminum cam work in a Sunfish. I think the factory threads are 1/4"-20 that is a little over 6mm. Seat QR units are usually 5mm and drop right in. I think mine is a Trek system 3, but they are all similar.
It should not thread into the gooseneck. The gooseneck threads should be drilled away. The stem of the adjuster screws into the “nut” that comes with the adjuster - not into the gooseneck.Well, I've got a quick-release here that I actually bought on this forum and it will not thread into my gooseneck, so they can't all be the same.
Sounds like you got one with a 6mm shaft. Just drill the old threads out of the gooseneck with a 1/4 " drill bit. Don't worry about it being permanent. Once you have an adjustable quick release, you will never go back to using a sharp screwdriver next to your sail.
linky...description...not trying to undercut anyone....8 bucks for 2 from amazon. not stainless. i might not use stainless anyway in case of galling. but test fits in the shop pretty well.
Yes. Allows for easy adjustment of the boom for varying wind..Otherwise you need tools..Out of curiosity, is this to make adjustments of gooseneck positioning easier for adjusting sail position for different wind conditions?