I have a large Clown Trigger living with a mature Volitan. You are correct to show concern about the Volitan fins. The Clown Trigger is one of only a handful of fish that can destroy a Mature Volitan (Cornet fish, White-tip shark, being a few others). The Clown Trigger will start by plucking out the venomous spines, rendering the Volitan defenceless, and then slowly dismantle it.
I am constantly looking out for any early signs of this happening, and am aware that sooner rather than later I will have to separate them.
One more thing, was you aware that when a Clown Trigger attains its full adulthood they can turn during the night, and destroy every living creature in the system? Fish, inverts, and corals, nothing will survive. I bet I have opened a "Hornets nest" telling you these facts.