Super Galaxy Gurren Lagann was fighting. That thing is established as being the size of the moon
I think your talking about a different gurren lagann form (though you could be right looking it up)
Though I don't think that argument holds much merit consider how Gurren Lagann sizes jump.
--
XBL GT: Demon Ninja X2
"There comes a time in every man's or woman's life where they have to make **** up to cover their ass." - Hazama