fu mans have short fins, they won't draw as much attention as a volitans with the long flowy fins. I've never had one myself (because triggers are evil) and I've surely never mixed the two, but I've heard a lot of people have had the meaner triggers chomp on the lionfish fins.
But aside from that, I'd really not put a clown trigger in a 90gal. I think you'd have one vicious, large fish in a too small tank with a lot of pretty fins flying around. Just asking for trouble. Perhaps the picassos are more docile, and I know they're a lot smaller.