Some of the people who commented stated that they either hadn't thought of that, or that they agreed because they too had to sleep diagonally. Back then, I wondered if we ever actually saw it in the show - in Scarecrow and Dead Man's Blood, he is sleeping straight, though possibly with bent legs...in Dream A Little Dream Of Me, he falls asleep half-way off the bed.
Then last night I was capping Death Takes a Holiday for the clothing project, and saw this:
Look at him! He looks like he's in a bed from Munchkinland. :-P
Incidentally, I discovered that there were more dates in that episode than I originally caught (that's what I get for doing my rewatch on the crappy TV instead of my computer). So, the Timeline has been updated with alternative dates for episodes 4x11-4x16 (Family Remains to On The Head of a Pin). Basically, I've included two options that you can mix and match as you see fit.