Andy, Do you have a link to the chart?
Anyway from what I always understood, the problems are if the "small valve", is too small for you because if the surgeon gave you a smaller valve than they should have, and a bigger one would have fit, then you have the "the mismatch". BUT IF that is the correct size that is replacing another "small" valve you were born with, you wouldn't have the same problems.
Also I would think what COULD make a difference is compared to the rest of your heart, is the Aorta and valve what would be expected OR is the rest of your heart and valves bigger to go along with your height , but for some reason just the Aorta and valve are smaller than what is average for a person your size? That would probably be easy to see from your echos are all of your measurements at the low end of "normal" , you just happen to have a smaller heart, OR does the rest of your heart seem to be average size or slightly above average (since you are 6'2) but you just have a "smaller" Aorta then one would expect. I could see that causing problems with blood backing up into your heart ect, but you would think IF it was small enough to make a difference, at 49 you would ready have problems (beside the ones you just had fixed), and since you don't, I would take that as a good sign
Some parts relating the valve size of BSA don't really make sense to ME. I could see the formula working if you (anyone not just YOU) were the average weight for your height, like it would make sense a 6 foot person should have a bigger heart and valves than a 5 foot person, but It doesn't make sense that if a person is overweight they should need a larger valve area, then if they lost the weight.
I think you have the right idea about asking your doctors their thoughts and anything you should watch out for.