yellow tang verses copperband butterfly

[howdy20012002]

i have a yellow tang and and a copperband butterfly.
I tried to put the butterfly in a 90 with the tang and it got the crap beat out of him.
how much abuse can a butterfly take? it was mainly just chasing around but the tang would occasionally hit him.
I built a cage out of eggcrate and was going to float it with the copperband in it for a couple of days to see if that would work..allowing the fish to get used to each other without hurting each other.
Any other ideas?
or should i just look for a new home for my butterfly?
What are the chances that I could come home to a dead fish?
any help would be appreciated.
thanks
Neal