A point of comparison,or not.
The heat load is based on cubic area among other things. There is ~60% difference in the size of these two structures depending on the actual area of the cathedral ceilings in Mark's house.
I ran an on line heat load calculator for two simplified structures with the only differences being location and size. 30x60x8 in Deluth, Mn. and 50x50x9 in Evansville, In. The In. location showed a 13% greater heat load, accounting for climatic differences.
Of course this does not really tell us anything, but concluding that something is wrong with Mark's system may be a bit premature based on the very simplified data set provided.
Having it checked by a third party is a good idea, especially if you have a competent 3rd party. I had an energy audit run on a customer's home we were doing some unrelated remodeling on about 15 yrs. ago. The tech found a large ~.5ft/2 hole in the return air pulling unconditioned air out of the attic. This was about a week after his AC tech had checked out and blessed the system.
