Just finished a big remodel on the house. As a result, I have to crawl
about three times as far in the crawl space to change the furnace
filter. Our furnace guy told me that I could install the filter behind
the grate of the cold air return (the opening's big enough for a 14 x
20 filter; the one under the house is 16 x 20). This sounds great to
me, and a simple fix. Is it as simple as installing a frame to hold
the filter behind the grate?

Thanks.

Lynn Willis