Andrew,
One thing to always consider is the inside diameter of os Venturi are not all the same . I have seen stock os Venturi on la 46 and fp 40 range from .285 to over .300. , the fp 20 and 25 seem to be more consistent, andi will matter what size and brand nva you are using ,
Sometimes when people tell you a specific Venturi type or size, they do not mention needle valve assembly or the actual Venturi size,
I just changed a la 46 from .288 to a 265 Venturi, with supertigre nva , ran great on a little less than 4 ounces , 12 / 4 APC prop, just like Ray did, and his do run great, main reason for change was limited fuel tank capacity.