When I did my SBS a while back I used first initial, middle initial, last name, city and state. I do not think that ATF is too picky about the markings as long as it is accurate. I have never heard of anyone getting into any kind of trouble for incomplete markings. Heck, there are a lot of folks who do not believe they need to put their info on the weapon and I have not heard of any of them getting in hot water with ATF either. Just my opinion, YMMV.