The overheads are massive. They just need to encourage their use.
I have travelled on many where they are total full.
But I can see us getting to the airline debate of should the handbag / jacket be under the seat. You are correct of course larger suitcases fit. I bit of overhang so I was concerned if a jolt may result in it falling out. Probably paranoid. Likewise i suspect many passengers may not physically be able to pick up.
I am hoping the removal of those seats LNER propose will be enough. This week is a good test. But it is correct to say they have more space than many modern trains. Just the system used on the 91s / HSTs worked well. So it will take time to retrain passengers.
So it could be interesting in the next 2 weeks. Although the majority of Anglo Scottish services are still 91 operated so possibly “nothing to see”