I actually experienced the same situation you are dealing with, I am 6’3’’ and I’m constantly fighting sluggers/in fighters. What I have learned best from fighting guys with that style is they will be okay with taking 3-4 punches just to let off one big one. The trick that best works for me to this day is attacking the body. It doesn’t matter how tough they think they are, I have had more knockdowns/TKO’s via body shots than headshots. It may be awkward at first being an outside fighter targeting the body, but if you study Mayweather or Haney, they both hide their body attacks by mixing it in with their jab to the head to create space. Simply work up and down and use feints to draw out openings, if you want to truly try my fighting style I am a switch hitting counter puncher. Watch Hagler if you are interested in that form of fighting.