I have been using the EVO RNV on most of my 40 class motors to get the needle away from the prop:
https://www.google.ca/search?q=evolu...w=1280&bih=599
Think I have at least one more in spares, (intend to do that mod to a NIB OS 45FSR getting mounted to a -190 this afternoon so hope there is another).
I should at least check there is a good seal with the cap bolt and may fab a gasket for that one, as well. Would like to compare the two carbs. Biggest problem is the need to remove the engine to get at the mounting screws.