I already had the slim digital ballasts and I got my bulbs from DDM, 5000K and they came with the rubber rings around each bulb wiring. I took scissors and cut straight into one side. Once I broke the circle, I then took the scissors and cut the rubber ring that I needed and it did fit into the housing, like it was made for it. I then took one of DLF's adapters and put them on top of the rubber to seal out any moisture.
As for the screw size, I ended up finding some here at home but still cracked a few holes but the bulbs are being held in tight. It's nothing that JB Weld won't fix, if needed. I wished I had taken one of the housings inside of Lowe's or Home Depot and dug around until finding exactly what they needed but I never did. Now that I have them in, I'm not sure that I'm even going to keep them. Thinking about selling the housings, bulbs, and adapters. They might look good in the daylight but my new halogen housings with 6000K HID's put out more light IMO. I'm not too crazy about the HID housings. I think they're overrated.