So did you get that done? That was a nice solution offered to you by the dealership, I like that they offered that to you. If you had this done - Did you have just the passenger headrest modified, or did you get both modified so that they match?
When I ran at the autocross, it bothered me, but I became so focused on driving I didn't notice it too much. If I really started to autocross a lot, maybe I could buy a new headrest (if it's not too much) and just swap that in for when I have a helmet on..
Post some pics if you had this done!!