You can either go get him (head movement, aggression...think Tyson, Marciano, etc) or make him come to you (Sergio Martinez, Jean Pascal, Joan Guzman, etc.) Being shorter DOES NOT mean that you have to go hunting the other guy down. A lot of guys find more success by making the bigger man come to them. I got my ass handed to me in my first fight by a guy who was about 6 inches shorter than me, and I doubt he took more than 10 steps forward in the whole fight lol.
Hey, saw you were posting here the other day. Always good to have people who know what they're talking about here lol, post some knowledge for us!
It will help with stamina, but doesn't necessarily mean it will help you improve on what you are looking for, which is the ability to get inside. One thing my coach always told me, who absolutely drilled inside fighting to the point of nausea was to get small and "bend your knees" when getting in.