Flynerd, think you hit it on the head.
These new weight/space saving devices are great in the purfect world, and that is the problem, we not in the purfect world.
Excuse the slip, but the 717 was developed because we don't live in the purfect world, fuel prices went up and the 717 was put out to grass.
Lets hope jet fuel slips back to $10 and the 717 has a fair run.
The cost of having these lightweight items fitted/re-fitted to aircraft looks like it may out weight the fuel savings in the future.
Keep yours eyes open for the next AD...it can't be far away.......