So the studs arrived yesterday, took about 10 days to get here from Australia. Cheers to Pentastar parts.
So I put one in and it looks like it should work. Like I suspected, the shoulder of the stud does indeed end up lower than the flat surface of the hub. There is a slight chamfer on the hub surface where the would be no clamping surface with either stud in place. The shoulder of the longer stud is slightly below that but not a significant amount, maybe a mm or two.
The stud pressed in with some resistance so its in there solidly, no wobbling or anything. The knurl is the same diameter as the OE stud. There is a slightly larger step right under the head but they are essentially the same. It sticks up about an inch and a half +/- above the hub surface.
My hope to use open end long shank lug nuts may not be a possibility because the studs aren't long enough to stick through the open end. They do thread in to the hex portion of the nut though and the shank is threaded all the way up so there is plenty of clamping surface and the increased mechanical advantage will be the largest benefit. I will have to check the specs on the Centerline lug nuts to see if they're worth getting.
Anyway, here are some pics. Hope this helps anyone thinking about doing this.