When using Farmer's Delight tatami mats, it did not give me the original feeling of stepping up (agaru). In Vanilla I am used to use birch slabs instead: a bed surrounded by birch slabs looks like a futon. So when tatami mats would have a heigt of 5 or 6 pixels instead of 2, the wooden part of a bed would be covered and therefore a bed surrounded by 5px tatami mats looks like a futon as well, as (create-/quark-) seats would look like floor cushions.
In the screenshot I changed the model in my personal ressource pack accordingly (but not the hitbox). (Damn, I stepped on the tatami in my shoes...)