Lots of people think like this but I have other opinions but either way.

Is the OP's car a race only piece?

Lots of people tune stuff different ways. Some still use total timing as the method on a car with an advance curve, even though cleaning up the idle characteristics can help the car leave on footbrake. Lots of ways to skin the cat.

My deal with a PV is to NOT have an extremely low numbered PV, 2.5, just in case the engine starts pulling a vacuum at high rpm/WOT conditions. That's where the select at idle using 1/2 vacuum guys can get killed. The time difference between a 5.5 and an 8.5 opening when you drop the hammer is so small it's not anything to worry about, manifold vacuum drops to nothing. Watch a gauge how fast it passes through the range when it's matted.

I've got some holleys that the arm on the throttle shaft has become loose. That actuates the pump cam slightly before the plates actually open. Make sure the gold arm isn't loose on the shaft.

Try disconnecting the secondaries and dial in the primary pump shot. Hook secondary up and see how it goes and tune that side. Trying to do both at the same time can be frustrating.

As far as the OP goes. Put an AF gauge in it to see what's occurring. Great tool to diagnose issues.

Ya, I need a clean cruise AND plugs and now mine look like new after street driving and street racing...........

Here is my experience with the power valve opening point for a street car;

When cruising in the 14.+ range, a late opening power valve (6.5 and lower numbers) can often result in a stumble with light additional throttle. 14+ A/F ratio quickly becomes 15 or 16:1 under even light additional load without additional fuel.

With an earlier opening point (8.5-10.5), the additional fuel comes in at a more appropriate time and prevents the stumble.

I do agree that when you stomp it (whether at the track or on the street) you blow past the opening point fast enough that it is far less relevant. But can still help or hurt in some situations, so it should receive some attention.

Most of the Double Pumpers I have dealt with have been plenty rich about everywhere, so I would be a little surprised if the OP's DP needed anything more than a bit of tweeking, if in fact his stumble is due to a lean condition.

Just my .