ALWAYS have the bucket lower than the fermenting vessel. IF at all possible, put the bucket/bottle/etc. on the floor. You do NOT want to get the stuff from the blowoff bucket back into the fermenting vessel.
At most, I've used a milk crate to lift my blowoff bucket so that the tubing was going into the sanitizer solution (Star San). If the tubing was longer, or not so twisted, I would have put it onto the ground. This was taking a feed off of a 1/4 barrel (tall) fermenting keg. So the tubing was about 24" above ground level. The bucket, and end of the hose, was about 12-16" above the ground.