Change monster size?

maybe, depends on the monsters (if its BOSS) maybe not, but u can edit the .BMD files of monster from mosnter folder in client/data/monster
convert - reconvert with pentium tools cracked by xakumm (search it here) and convert .bmd to .smd and use milkshape 3d free from google download it, import smd and animations and u can scale etc maybe and save it, but i think there is auto calculation of boss/event mobs etc since i tried with Balgass and didnt work well (more bosses came lol 4x) bit glitchy buggy, but u can try anyways.