if you're average for your height, and these tall guys are musclier than you... shouldn't they be heavier than you?

If some one weighs as much as you and is tall than you, 9 times out of 10 they are skinnier than you... just one of many reasons why you should fight in your range and no theirs, you can really hurt them to the body and can hit harder on the inside.

Practice your head movement and footwork, come forwards and move your head past the jab... once you're inside... WORK!