Lastly, I have an old RCM magazine with a construction article for a .40 sized floatplane that the author fitted with one of the early OS Wankles and he speaks of it having a factory nipple on the engine casing (but no provision for a nipple on the muffler!).

There is a nipple on the engine and although it is not mentioned in the Wankel Instruction book it serves the same purpose as the extra nipple on the bottom of most four strokes. The nipple dumps the excess oil that accumulates between the back bearing and the backplate. It is not a pressure tap. Trust me.