Looks like your are going to have a couple of of extra steps in the shoulder. ? Where you have the word curl, do you mean knurled?

I spoke with ARP at length again today. It may look different but that is due to the poor manufacturing process of most studs. The Curl is pressed into the stud which causes the spike to flair out making that section/curl the final size.

ARP cuts the curl into the stud for more straight/better quality and there is no reason to have that one smaller section and not just extend the curl. The forward section stays the same. Every diameter change cost $$.

Also keep in mind that the drawing is not to scale. Even on the stud you pictured there are steps. .27mm and .67 mm is very small but are in the stud.

And yes it is Knurl. I have also heard it called Curl. Oppps? 

couldn't you send them a factory one and tell them you want it longer, just to make sure they make it the same?

The above drawing is the same as a factory stud, other then the above mentioned step. If you are going through the hassell of doing this why not make it as good as you can...