I'VE GOT THE FIX!!!
* Instead of 2 sticks butter, I used 1 stick (unsalted) butter, plus 1/4 cup of the butter flavored Crisco (which was one quarter of the individual little bars they come in.)
The only other small things I did differently... using a lower speed on my mixer, and sifting the all-purpose flour before measuring. I did pack it down somewhat when measuring also, but stuck to the 2 1/4 called for. I did not need to chill my dough. I tried with and without parchment paper. It worked fine both ways but slightly better with the paper. I reduced the time to 8-10 minutes.
The results were perfect, and the solution was so simple! I do believe the butter alteration was the one thing that made the difference. I was concerned that they wouldn't taste as good but they taste wonderful! Hope this quick fix helps anyone else facing the flat cookie dilemma!