Disclaimer: I have no amateur experience nor formal training background. I am more or less self taught.

I spar with a guy who has 8 inches on me and I find when I move well laterally and get low, it frustrates him and he begins to throw angrily. I use this to slip/bob, get inside and throw at his body with bad intentions. He countered this by clinching and laying on top of me. I countered that by either landing my shot on the inside and stepping out of distance (ideally laterally and not straight back) with a jab or surprising him with a leaping left hook over overhand.

I noticed that if I fight in a straight line, he feels real comfortable just leaving his lead hand out and I have to exert more energy to get inside. I also try to make it a point to control the center and not get myself backed into a corner. I try using feints from different angles and establishing punch patterns to break them seconds later.

Some times I'll even throw at his hands as I'm moving in to occupy his guard and land a shot from a low angle.

tl;dr be real confusing and unpredictable.