Sar, Mongo has modified his 14EII and 20EIII to fit any Nikon lens. Mongo was surprised you have not modified yours. It only takes about half an hour each and you could not even tell where Mongo had performed the surgery. Mongo is happy for you to look at his and use them if you like. Then, if you want to modify yours, Mongo is happy to help you with that. Being able to use these converters on Ai and AI-s lenses may give you a lot more options.
PS - MOngo also has a newly acquired "Vivitar X2 Macro Focusing Converter" (from the 1970's) he would like your opinion on. It can only be used on Ai and AI-s lenses.