Those would help for about 5 seconds or so. He's not a trained boxer so he wouldn't know how to properly use the reach advantage to keep Tyson at bay.
Shaq holds his arm out, Tyson merely use his honed speed to get under it. Shaq tries to jab, Tyson ducks and moves in anyway. Shaq commits to a haymaker, Tyson sees it coming a mile away and waltzs in for a crushing blow to the body.
Mike Tyson is built to take hits from other PRO boxers. All Shaq could hope to do is get a lucky glancing hit off the top of Mike' head. But, by then Iron Mike is already up in those VERY SOFT guts. One hitter quiter to the body.
DING! DING! DING!