Totally feasible. Keep in mind everyone is different. Some guys are great length gainers, some great girth gainers and then everyone else. Set realistic, achievable goals such as three years of steady exercise and you just might surprise yourself. Take lots of pictures along your journey, especially during the first 3-6 months so you atually SEE the difference and not only by the ruler.
Also, get in the habit of measuring correctly from the start. Measure from the top and push that ruler into the Fat Pad (do a search on proper measureing). Nothing is worse than finding out your were measuring wrong in the first place and then realizing halfway through the Newbie Routine that you may have actually gained more. Believe it or not but I think I gained more than I claim because of my stupid measuring. For consistancy I’m sticking to what my signature says.
Good luck and keep up the good work.