Good answer Jim. I spend too much time looking for structual defects than to trying to calculate heat loads in the house. You are right about the fact it sounds like the installer is wanting to pull more humidity out with a larger condensing unit. They make a lot of systems now which are universal so the companies do not have to stock so many different sizes in stock. Usually the equipment comes with a couple different orficies to size the output, even fan speed controllers. I have been troubleshooting problems with a rather large house that contains six geo thermal heat pumps that the owners say it never gets comfortable in. I have found that the installers have installed 3 - 2 1/2 ton cond. units to 4-1/2 air handlers, a 4 ton to a 4 ton, 3 ton to a 4 ton and 2 ton to a 2 1/2 ton. The company made several attempts to repair this system to no availe and I wonder why? got my work cut out for me.