Why else would they make triple carb manifolds!
P.T. Barnum said it best- - - -"There's a sucker born every minute"! 3-carb manifolds are made to make sure "A fool and his money are soon parted!" Just because some dummy can bolt it on is no guarantee it will ever get out of its own way. One of my friends set up the exact same thing you're describing on a 51 Chevy 216 when we were in high school in the early 1960's. It was easy to find his car after that- - - -just look for the three burned spots in the hood from the carburetor fires!
Jerry