That's sweet. We've had up to 4 people at one time on my 9'-2" longboard before. There was only 1 guy in the mix, for the record.
Here are some friends of mine behind a 36' cruiser with twin 454 V-drives. Both sides are surfable. The guy doing the transfers (Hunter) is a good rider, and makes them look fairly easy. I haven't gotten to ride it myself yet. :\
http://www.youtube.com/watch?v=_Fu-lUT4_-U