In tfc and tnfc getting in to the bed to sleep is hard, you take a little damage and instantly get kicked out, after several tries you can eventually get in.
In tnfc i put the bed at 99 and could get right into it.
If Y is the vertical then yes, didn't want to get them mixed up lol.
Ah. Right. Z coords. Anyways, IIRC the bed problem was fixed at one point several builds ago from some nifty config changing. I recall it had something to do with how essentials interacted with TFC. Between essentials and worldguard, there may be a way to prevent the bed kickout issue.