Hi Ed,
You lucky man ! I've rang round almost every major R/C shop in England recently and cannot find a Hog Bipe in stock

Pity Tower Hobbies won't ship large parcels to the U.K. as even when I do find a Pig it could cost me up to £130 (approx $200 !!!).
From what I have read I believe Lownslo is quite right about fitting as large as possible wheels and moving the landing gear forward to avoid tip-overs and improve ground handling on grass.
Moving the C of G forward will affect the flight characteristics making the plane more docile/stable. Slowly moving it rearwards, flight-by-flight, after you are use to flying the bipe will increase it's manoeuverability to the point where it becomes unstable. Or so I've read
Have fun and let us know how you get on. Hopefully I'll be following closely behind in the building of the Sig Pig.
Steve