I'm convinced after having five (maybe three if Sears and Home Depot don't count) installers look at my replacement installation that they simply don't want to spend the time to do it right. No one has even suggested that they would do a Manual J after award to fine tune the size of the furnace. I told the last installer about a heating problem in a small addition that apparently had not been adequately ducted and he shotgunned two or three "more is better" suggestions for adding ductwork in the attic.
At this point I've decided to pick one that I'm comfortable with who seems to offering a fair price, but tell him he has got to do a Manual J to correctly size the furnace and do do a Manual D (is that the duct calculation?) or equivalent in order to improve my ducting without overkill. I'm more than willing to adjust his estimate based on the results, but I don't want an oversized furnace installed.
Does this seem like a reasonable approach?