i thought chainsuck was when the chain gets stuck on the chainring you are in, and continues to wrap around the ring causing the cranks to stop turning. i thought its caused by worn rings, and/or mismatched components (new chain, old rings)
the chain dropping off and getting stuck between rings is not chainsuck. from what i understood chainsuck has nothing to do with shifting either.
i used to have a gary fisher big sur that had built in adjustable chainsuck plates. it was cool, but i never had the chainsuck problem on that bike.
anyhoo, correct me if i be wrong