Woodstuff makes a real nice tunnel for gassers. There is a company in Germany, OSSI, that makes a sweet looking glass boat. Aeromarine's Predator X needs help in turning. One Predator at the National OB Champs was able to turn ok without the need of a turn fin. This was done by moving the motor further back. The Predator has an inserted transom.
As Ronald suggested, perform a search on Gas Tunnels here. There a few posted already.