you can use growfs in SVM (disksuite)
if you use growfs -M, you can grow it while it is still mounted. I've used it many of times, it is pretty straight forward.
your biggest probelm is your metadb's are sitting in the middle of your disk, as you said, you should move them to slice 7, maybe you can delete the metadb's on ONE disk only, and move them to slice 7. At this point you can attempt the growfs command, it is hard to tell w/o seeing how your disk is actually laid out.