Now that I know some others in real life who know the same stack as I do, I'm interested in doing a partner act taking advantage of that. I'm sure others have already done some thinking on that. Any resources?

What are some fun ideas to do with two people who know the same stack?

There are two ways to go about that:

1) the specs know you are both performing together; or
2) the specs have no idea you are in cahoots--they perceive a performer and a fellow onlooker

#2 has the potential for a lot of deviousness...

For example: A hands off-ACAAN: A card is named by a spec. The magic partner names a number (the stack # of the choice). The performer splits the deck in half and hands the half with the choice in it to his partner, and the other half to the spec, with directions to shuffle. Your partner false shuffles, keeping his half-stack intact. The performer reassembles the deck, places it on the table and asks the spec to count down to the number...

Check out Simon Aronson's Any Card at Any Number from his book The Aronson Approach.