I only ask because I initially set my PV by going with 1/2 of the idle vacuum. I ended up with a 5.5 using that method. It had a mean lean stumble when accelerating from cruise. When I checked, the cruise vacuum was 18, so I switched to higher PV. The highest I had was an 8.5, so I threw it in and it eliminated the lean stumble completely. It would probably benefit from a 9.5 or 10.5 even.
Another question is how much initial timing are you running, That seems like a pretty big drop in vacuum from neutral to in gear. How much rpm drop do you have shifting when into gear?