I've done a bunch of reading on filter systems for home and shop. My home HVAC uses 5" filters. I'd like higher MERV rated filters, but the load on the fan motor would pose an issue, UNLESS I added even more area the cage could pull through. That is, I'd add three more filters.
The design for holding them is such that I can put cheap 1" filters in front of them to catch kids, cats, hair and other large things that would block expensive filters. I'd do this with a square frame with the center cut out and long bolts (allthread) and jig knobs.
With triple the air flow area, I figure I could go up a MERV rating. Just as my "four bag" collector with two cannisters, instead of bags, draws far better than my "four bag" with four bags.
To test results, I started with a manometer, but was pointed to Magnahelic gauges [on EBay] and I have haven't looked back at the fluid system, for the house.
For the shop, again, the gauge or meter has to be in front of the filter, rather than between the filter and squirrel cage. That's a LOT of pressure, so I'm looking at an IV type control to limit how much the system can pull on a manometer, or even a magnahelic gauge.
Anyway, any shop MERV filters will only be for scrubbing the general shop air and will never be used for equipment or toll dust collection.