Several members here have done the conversion. The old stat must be substituted with the 'dummy' or orifice plate in order to seal the housing. The 'dummy' is simply the old stat outer disk which bears the seal as I recall. I try to locate details. Get new from Rimmer, etc.
See Item 16 here:
https://rimmerbros.com/Item--i-GRID001696
Whether it's worth doing is a matter of opinion I'd say. Some think the K16 can't be fixed in the context of heat control no matter what's done with it, while others reckon this kit is just what they need. Your money, your choice.
Search:
https://cse.google.com/cse?cx=013872...69.pvylGfJCAqU
TC