The consensus on the max MERV 1" filter from most pros is a MERV 8. I''ve followed this religiously w/my filter purchases for my Amana ASZ 18 HP.

Now, I'm considering moving up the filter grilles or grille filters (?) of the 4-5" thickness.

Question: b/c its NOT a 1" filter, can I increase the MERV rating from 8 to more, while maintaining just as good or better air flow?

In other words can would a MERV 8=MERV 12 in a 4 or 5 inch.