I think there might be a size limit, but other players cannot see you, and it could actually be considered cheating, if you can make an oozaru that big, since because of the hit boxes, you'll be able to aim up at their huge, towering head, and blow them up, when if they were a normal sized Goku, you would have missed. But I don't even know if you could do that with ESF models. I know you could do that in HLDM models (not the most sporting thing to do, make a huge model, then replace all your other models with this huge model, then kill everyone easily, since they are big targets).