No, not arbitrarily, but a long time ago as a Heil dealer the factory advocated cutting a new return up-stream of the CA drop. The idea was to get the new grill away from any other gas appliances to prevent a negative pressure zone that could cause flue back flow.
This would afford some increase in in return air flow and some times cured the problem completely. Nowadays, the purists would a call that a hack's approach. It had one drawback that could affect home comfort and that was the temp of the basement. If a home's cellar is colder than norm, the new RA grill could add to the home heating load by pulling in cold basement air.
I'll still use this method today if there is no other alternative.
This would afford some increase in in return air flow and some times cured the problem completely. Nowadays, the purists would a call that a hack's approach. It had one drawback that could affect home comfort and that was the temp of the basement. If a home's cellar is colder than norm, the new RA grill could add to the home heating load by pulling in cold basement air.
I'll still use this method today if there is no other alternative.