This is true. The rooms have less storage space for bags than coach.
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This bag, plus a daypack, pretty much maxes out the carry on baggage allowance for the sleepers. This particular model folds up and packs in a nice storage case, so when didn't need it, it didn't take up too much space.
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This is the cabin for one (roomette). The bag is sitting on top of the commode cover, but that's where the bed folds down. At night, it will need to go under the seat or bed.
Fortunately for me, I was upgraded to a cabin for two (bedroom).
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Looks like a lot more room, no? but there's not place for the bags except the floor. You can't even stash them under the bed at night because the chairs fold up and are stashed under the bed at night. The little cubby over the restroom can barely hold a toiletry bag, certainly not a backpack or travel bag.