I saw these HDR 4 1/2 inch deep pleated filters just out by Flanders when I was in Lowes buying the Energy Aire 20xx20x1 filters for my Trane 3 1/2 ton system dual fuel. I have been following the advice of people on this forum using a low merv rating but high enough to cut down on the dust in my air/house. The regular filters I have been using are rated 7. One person recommended I use the green Natural Aire from Home Depot, rated 8. I am using both. I have three returns. Do you think these new deep filters that fit into the same compartment as the regular filters would be advantageous OR would they put too much strain on my system.
As a check, do you think what I have been using is too much strain on my system as is? Two 20x20x1 returns and one 10X20X1.

http://flandersfilters.com/products/air-cleaners/