I concur Ken. I think it's misleading to assume a stronger vacuum signal from a ported connection. Unless you got some really 'special' port the vacuum signal should be the SAME as intake manifold vacuum IF the throttle plates are even slightly open. I just don't see this signal increasing as a result of higher air velocitys in the venturi area of the carb as rpm increases.
Should be easy to check with TWO vacuum gauges, but it might be difficult to interpret the results. Vacuum gauges are as much 'art' as they are 'science', tricky stuff.
The beauty of a vacuum advance is it will NOT add it's advance to the base and mechanical advance when the engine is under load (throttle open). Other wise it WILL add it's advance and you can and want TONS of advance under 'light load' conditions, such as cruising. Step on the gas, vacuum drops, vacuum advance goes away as load increases. Perfect!
I like Fords thinking, go intake manifold vacuum, adjust idle speed and cure any 'run on' condition before it even comes up!