Yes, it would be difficult. I've looked around and have found limited options-mostly ending up with a roll bar and harness, something too radical for my taste. Harness? Yes. Roll bar? Not if I lose my rear seats. Wish I could just bolt the dame harness to the floor, loop it up through some Rocarros and be done with it!
Let me know if you come up with something. PM me. Very interested.....