Changing a cham's world is a big stressor. His whole climate and temp regime has changed, locating feeders is different, and all his memory of his space is no longer useful. Chams get to know their territories a a very detailed spatial way and don't trust "strange" branches or routes of travel. He probably feels that he's been dumped into another male's territory and he's just waiting to be kicked out by a rival who hasn't shown up yet. He may also be seeing new "views" of the room and there could be new reflections or other activity he's not used to seeing. Hanging around the bottom of the cage could mean he's trying to get out and find his old territory. In the larger cage does he have the same amount of thick foliage to hide in? He just sounds nervous, intimidated, and I suspect hanging the way he is means he's trying to be ready to escape at a moment's notice. When a male cham "loses" a territory fight he drops off the branch, goes low to the ground, turns a dull color, and slinks away from the winner. I think I would add more cover, maybe drape a sheet over part of the cage, check your temps and humidity to see if they are much different from his old setup, and leave him alone. If he's basically healthy and has good body weight he can go quite a while without eating much as long as he is basking and drinking. I haven't had a veiled in years and don't remember when the males tend to start looking for mates. Maybe this is the time. They don't eat much and are preoccupied.