This is a replacement for the fancy Severne RDM extension widget to adjust the extension height.   While the Severne collar is fancy, if the rubber band breaks (very easy on rig down), the collar just falls off and gets lost.  Easy to do and now you can't sail.  

This is just a simple Collar and pin adjustment system to replace.  Being Severne, the pin size is not ¼" like all other extensions but something like 7.25mm diameter.   To make the pin, I used 6mm stainless steel rod (seems to be common size in inkjet printers so salvage these rods if you are chucking out that old printer) and sleeved it with 9/32 x .14 Brass tube from hobby shop which makes a snug fit.

I printed in PETG at 100%, appears to do the job but haven't tested longevity.  Certainly will get you sailing again in less than an hr.   It's a nice snug fit on the extension, depending on the accuracy of your printer you may need to sand slightly if too tight.   The anti rotate divots where the pin sits are suited to the larger Severne pin.  Will post the standard collar shortly with smaller divots.

Whilst you don't need a leash for the pin its a good idea as easy to loose.   I used diabolo string for leash as super strong and lasts long time.  I was lucky that the stainless rod I had salvaged already had a predrilled hole.

Edit June 1: Extension has survived 5 sessions so for sure will last long enough to get you sailing and may be permanent solution??