Katsuya original size is same as Hashirama budha summon because while Katsuya was assisting Tsunade and other hokages,it was helping Sakura heal the shinobi alliaince (about 1000+ shinobi )against jubito.Plus Katsuya original body is in it home forest
Katsuya defense against Hashirama summon ,particularly Budha summon:
Katsuya have a special ability that allow her to split to any size it want.This is a very good evasive skill to counter the budhaa 1000 or any of Hashirama summon since they donot perform any jutsu.
Katsuya offensive abilitiy :
Katsuya can shoot or spray acid on anything and it will break down within seconds
Even a master regenerator like orichimaru can be kill by Katsuya acid release.
If Katsuya in it orginal form (full katsuya size) spray acid on the statue it will destroy it.Katsuya can also destroy the statue by dividing into smaller size and attack at every angle of the statue with acid.
I know alot donot like me here but i am using logic ,so please donot bash or flame me.