Well, the hoist height on my Nacra 20 mast is about 28 feet up, and since a 16 mast is only 26 feet or so...it'd have to be at the very top, and a long spin pole to boot (or a very loose luff).
Bigger is not necessarily better when it comes to spinnakers. On my old Nacra 6.0, I had a 425 sq ft. spin that was massive, but was much slower than the 350 sq ft. NE chute for the Nacra 6.0. Even now, my Nacra 20 spinnaker is only 270 sq ft, and is much faster than any of the larger 6.0 chutes. Stacking sails on a boat will not necessarily make it go faster.
[ok, I am waiting for MBounds to come in here and correct me on something]