I just measured using a plain wooden strut at its default size
this is vary simialr to the size of a sackboy
on a completely empty new level
you could fit 375 across and 192 high (give er take a few )
it takes 1 minute and 35 seconds for sackboy to run from one end to another
Doesn't sound that big.,....
trust me its a decent run from one end to another
esp when some person made a level with a broken vehicle .. its large enough to be annoying