I've got the vacuum outboard carbs and the only tunning I've done on them (besides idle mixture) is change the vacuum springs to get rid of the bog it had off then line. It runs good but I'm sure there's more there for someone that knows what they're doing. I've contemplated adding the Promax metering plates but wasn't sure if it was worth it or not.
I'm talking to Modern Cylinder Head about CNCing the MP heads. They have a program for the Eddy's and this is the same head.