Here's a few more pics of how I mount the drivers into my cups. I make the opening alittle larger than needed and put foam tape around the driver in order to snuggly fit the driver into the opening. Then I use a few beads of hot glue to secure the drivers.
1) Driver is alittle closer to the ear. Grado's generally are very forward, and I've found that this design is well suited to the Grado driver.
2) The driver is really easy to remove if you need/want to get at the back of the driver for modifications or a re-cable, etc.