My PM has spoken with the head dude in charge at Crown, who reports he has the famous 5 inch pleated filter in his own house. (Merv 10) Especially for our allergies, this is a good thing. You have to keep it maintained, though. They say to change it out every six months or so. My plan will be to check it monthly, when I replace the one in the basement. The basement filter should then be the cheapie one inch fiber filter with a screen backing. You can see through them and they are blue or green fiberglass-like mesh. It needs to be replaced monthly.
Big filter in the giant return air vent: Big honkin' Merv 10 pleated 5 inch filter. But keep it clean, kids.
Basement filter: Cheapie 1 inch filter, changed monthly. ours is 16x25x1.