Does anyone know at what position the secondary throttle plates should be in statically or on the bench.In other words what is a good starting point before trying to figure out a popping (intake backfire) as soon as secondarys kick in should they be fully closed or adjusted slightly open and how much? Before i get into detail about the extent of my t/shooting etc... It is a holley 950 dp mech secondarys with idle circuits in both metering blocks. Thanks Frank.

minimum air rate ( the opening of the secondaires) is as close to seated closed as possible without causing any binding.

Here is a bit of info I came across one time which tells you how to set the carb up. It actually says to set the idle by adjusting the secondaries.
http://www.candsspecialties.com/tuning.html