Since changing to the KN/Garretson type regulator, Jeff says he has noticeably better fuel economy and no running issues. Unfortunately he has had some very noticeable raw propane smell in the engine room. A problem for someone disabled with severe chemical sensitivity. The first obvious offender by stiffing while running was leakage at the carb inlet. We fixed that by adding 3" tube to an auto air cleaner housing mounted on the wall. Next we found there was a leak at the KN regulator. Internally, there's a sewing type straight pin through the rubber faced disk which seals the gas inlet. The pin head was not sealed. Gas was slowly leaking through and then out of the diaphram chamber. A simple dot of gray silicone gasket maker over the pin head stopped that leak; no more leaking with engine off but gas on. I suspect that parts or material changes over the years may have caused this problem with the KN regulators.
After this we still had a very minor leak with engine running, barely noticeable near the KN regulator. We traced this to the lack of a gas tight seal on the diaphram to actuating pin attachment; gas was leaking through the diaphram to the vented side of the die cast KN regulator housing. Fortunately, the vented side of the diaphram has two 1/8 NPT threaded holes. We plugged one, and connected the other to a 1/2" ID hose which we routed into the air cleaner housing. This eliminated that last of our leaks. I felt that venting the leak to the air cleaner was preferred over having to modify the diaphram assembly with new sealant and rivets, a fussy job that would have be redone with every new diaphram.
So while I think the KN/Garretson regulator is the way to go for the gulping Lister CS type engine, with gulping intake compatible CA110 gas carburetor, it does need these fixes to not leak gas into the engine room.