Yes, my recommendation is DONT do it. You'll end up having to use expensive 5 inch pleated filters that require monthly changing.
pleated filters overwork furnaces......takes twice as long to heat your house which in turn will raise your gas and electric bill....typically a 5 inch filter costs $25.00 each times 12 =$300.00 a year in filters YIKES.
Stick with the 1 inch use the cheap filters that dont overwork the furnace and empty your wallet...unless of course your just made of money in which case "where are you taking me for dinner and drinks"?
in all seriousness I see the repair/warranty and maintenance side of things from an entirely different perspective than any installer who just wants your money up front and doesnt care about any of the above.
Keith