I prefer to block off the power valve on my carb but I dont up as many jet sizes as most would. I bracket race and dont i dont run on the street and in bracket racing you want to be as consistent as possible so I run as lean a mixture as I can get away with which helps when the night gets cooler the car doesnt pick up as much with a leaner mixture. You have to play with your combo to see what works best for your application. All the Holley carbs I have run (all double pumpers) dont have power valves in the secoundaries not sure what your talking about there.
I would plug the primary and go about 4 ot 5 jet sizes up and go from there for track use but if your on the street you can go a few more, like I said before you have to play around with it to see what works best for your combo.
Goodluck, Charles