I just returned from Virginia Beach and checked out Austin's shop... he has some beautiful boards. Unfortunately, he didn't have but one paipo and it was pink. I think the posts you are referring to are older... probably sold by now.
I've never tried one but they look like fun. I'm getting too old to surf so I thought I would give one a try. I think Austin's father uses one. You have the option of fins as opposed to a boogie board. This is the description on website: "The Paipo is our version of a foam and fiberglass bodyboard. The advantage over the bodyboard is in the lack of flex, which gives you pure speed down the face of a wave. Another advancement is the fins. It comes with a 2+1 setup for maximum versatility. The fins allow tighter arcs and drive out of the turns. If you like to sponge, you will LOVE the paipo."
Here is a video link: http://www.youtube.com/watch?v=oCq_PB7jjSg
When I am too old to paipo it will be time for a longboard
Fin sizes and placement provide for different types of wave performance so experiment a bit. The stock side fins that come with Austin's paipos are okay for twin-fin riding but for a 3-fin setup try some smaller side bites in the 1-3/4 to 2-1/4 inch range and start with a center fin of about 5 inches and move it forward and aft to get a feel for the handling characteristics. If all you have is a 6" or 7" then move it forward and then start working back an inch at a time. My regular center fin these days is a 4.5" carbon fiber or fiberglass.
Also, the 50-inch baseline Austin has a much different feel than the Big Boy Paipo which is 52 or 54 inches long and a tad wider and thicker. Ideally the best "fit" is a board that just reaches the sternum (at or just below your chest). Have fun!