Since we're in the Racing Forum, I'll assume that you're application is a race car. My understanding is that you want the fuel delivery requirements of the primary circuit to be shared by using a PV and jets. This allows you to use smaller primary jets and thus, to idle in the pits and in the staging lanes without an over-rich condition that loads up your sparkplugs and burns your eyes. Once you're in the burnbox & jump the throttle this drops the manifold vacuum, and then PV would kick in to supply additional fuel with the jets. In the rear or seondary circuit, I agree you are better off to remove the PV (if you even have one there, DP'rs don't) and installing a plug or dummy PV. Yes, if you install a plug you have to install much larger 2ndary jets (maybe 6-8 or larger), but you don't need to worry about blowing that PV too, in the case of a violent backfire.

If you don't want to go with the plug in the rear, then I'd do as Holley does and use stepped PVs, to prevent a potential bog or stumble as a result of too much fuel coming on all at once. One example of this is in Holley's #3310, they ship them with a 10.5" PV in the primary and a 8.5" PV in the 2ndary circuit. Of course, barring personal preferences, actual testing is the best teacher.