I haven't fought MT in over ten years, but when I did I preferred the times that I just fought at whatever I came in at. I'm 5'10" and my first full ammy fight was against a guy much, much taller than me. He just kept me on the outside and I didn't get in and score well until the last half of the third round, where I kept him balled up in the corner and unloaded on him like a beast - I hurt him quite nicely too, but it was too little too late. From there on out, I spent a lot of time focusing on working the angles, infighting, and something we called "hacking" from the clinch. I'm not sure what the proper name for it is, but when they come in for the swinging knee, roll the shot a little and catch and pin their leg to your body, step your other leg behind their standing leg and flick it back as you drive forwards into their upper body and dump them onto the canvas hard. It doesn't really score but it's demoralising for them and if you do it nice and hard quite a few times in a round, it takes a bit of wind out of them. Oh, and low kick/overhand combos often tend to work well against taller guys IMHO, kick the opposite leg from the side you're launching the overhand from and a lot of times the chin will be reasonably open for you to drop a bomb on. Put that fucker down like a sick dog, man.
So, if you're looking at going into a division where you'll be shorter than a lot of the other guys that's some of kind of thing you might want to be thinking about. However if you're saying that you're a heavy hitter and rely on that as part of your overall game, I'd suggest trying to look to compete as lean and light as possible - this would be the best way to maximise your advantage IMHO. Of course you can possibly try to maintain heavier weight and just do a ruthless cut, but it's not fun. Doing albolene saunas with a bellyful of laxatives and eating nothing but boiled chicken breast for two weeks sucks man. Especially with same day weigh-ins, but if you can weigh in the morning and you're not fighting until that night it's manageable.