Here are some pictures of the Sennheiser PX100 II drivers in action.
My current pair "in use" as I work to finalize some last-minute decisions on the correct headband to use, along with completing a permanent cable for these. In this picture, I have the Auvio headband utilized (best $10 I ever spent), the Ear Zonk G-Cush pads (Best $19.99 I ever spent) as well as the Padauk custom crafted cups. In this picture, you can also see the drivers as they are present at the opening of the G-Cush pads.
Here is a picture of the driver set on the opening of the pair of SR-80i Grado cups. The existing Grado drivers were liberated from the cups and the Sennehiser PX100 II drivers are just sitting in place. They are about 1/32" larger than the standard cup openings, so one could just apply a few dabs of hot glue to hold these in place. I do plan on running a pair of the Sennheiser drivers in the standard plastic cups in the upcoming week so I can share some impressions on the sound.
Here is a picture of the Sennheiser driver set into place on a pair of Padauk custom cut cups. In this particular picture, one can see that a few small dabs of hot glue would easily hold this driver in place. If the cup openings were cut slightly larger, then only a single layer of electrical tape would be required to hold the drivers into the cups.
A little bit later - I have some additional pictures and instructions to post regarding the careful removal of the Senneheiser drivers from the PX100 II housings, as well as the proper labels to reflect which solder tabs on the back of the driver to utilize for connecting your cable leads to. Again, a bit later - but before the day is over.