From Mythic Enlarge Person:
You can increase the target’s size by up to two size categories, to a maximum of Huge.
The text for the non-mythic version of the spell has no similar restriction in the rules.
Assuming that Mythic Spells are supposed to be enhanced versions of their non-mythic counterparts, is there anything capping the size of a creature affected by non-mythic Enlarge Person, assuming he starts at Large or higher, and is Humanoid?