Mandy3206:I find the 9'-7" too big for me, but some offshore divers may find it useful in rough water.
http://www.omsdive.com/lift-smb.html
I guess it's a decision of easy to carry vs. usefullness. If the boat is close by those little 4' sausages will work fine. If you were really lost at sea, the bigger the safety sausage the better.
I carry a 10' Carter sausage in a mesh bag clipped to the bottom of my bcd just above my butt. It's totally out of the way, but easily reachable.