Originally Posted by cepheid

I think it's quite clear that common sense dominates. If you have no underseat storage, you can't be expected to store something there, so you use the bins. There is no actual rule about storing one item under the seat in front of you; it's just requested by the FAs and generally a courtesy to other passengers, to ensure that there is sufficient overhead space for everyone. If there's enough space after people are seated to put your second item in the bin, I don't see any problem with that. (But in your case, i.e. the bulkhead, then you have no choice but to store both your items in the bin.)