Actually that's MX's canon height. If Mario is 5'1 and the mushroom makes him 2× bigger that makes normal Mario with a mushroom 10'2 making MX only 2 feet taller then big Mario.
Yes,innocence doesn't get us far. I knew since i saw something related to the Man behind The skate. LOOK LUCAS,I'M SKATING TO YOU YOUR SHITTY LEGS WON'T GET YOU FAR OH,OHHH... AAAAAAAAHHHH !!! *Falls in an endless pit. Don't worry,he's alrigth.*