On this Trane Variable Speed Air Handler model TWE037E13FB, highboy, upflow, there is a vertically positioned Electro-Air electronic air cleaner. I have recommended removal of the cells due to homeowner lack of frequent maintenance. In the cabinet where the cells belong, I found a 5 inch pleated media (Merv 8) filter that will properly fit. I can also place a 1 inch pleated media filter (Merv 8) in the air handler filter drawer in the horizontal position just below the coil. In addition, I can also place another 1 inch pleated media filter in BOTH pre-filter slots on both sides on the air cleaner box. As you can see, this unit can accommodate a total of 4 filters. I realize that 4 filters are both unnecessary and redundant. I also realize that static pressure drop is not an issue with the variable speed air handler. The 1 inch filters would be cheaper but require more frequent changes than the 5 inch one. With all of these possible configurations, what are your recommendations for the most efficient (air quality and cost) placement of filter(s)?