I went with the white face. Not sure what size uni-bit I used. Did not get the install kit.
When using the step bit, drill slow to prevent porcelain chipping.
I enlarged the hole in a couple of big washers and, using a couple of sockets and a hammer, shaped them to match the arc of the dome. One on the inside, one on the outside, and used a "conduit nut" on the inside to fasten the thermo. Worked very well.