I can believe what i am hearing !!! Filter return should be sized at 2 sq in per ton?? right? Any one know the pressure drop on a standard filter???? Mfrs. are asking for a static balance of .5 .....oh not to exceed .5....... just found out my installers are using 24x24 RA filter grille for a 4ton ...and sizing the main supply at .1..... i can NOT get them to understand..... any ideas how i can get the proper static out of this mess??????