Ok I finalized the DTW5000 build (haha wut?)
I made some custom baffles out of some .135" ABS plastic with 8 vents in them. The paper covering the vents is COFFEE FILTERS! It works great, and they are easy to find anywhere. Thanks BlueMonkeyFlyer for the suggestion. I had to drill out 3 more bass ports on the sides of the cups to tune them as close to the original W5000 as possible. The W5000 cups have grooves notched into them at the very edge to make bass ports, which is something I needed to create on the DT770 cups.
These sound as great as they look, I promise. So Beyer owners, when one of your drivers fail, be optimistic and make something a little more interesting out of your dead headphones.
1, 2, 3 additional bass ports making that 4 total per cup.