When using the WPA (water pipe adapter) for the Silver Surfer, do you recommend a smaller or larger water pipe to hit through?

This is all up to what you like best.  We find a rig you can hold in your hand seems to be a great experience.  We have used a Surfer in a 6 foot water pipe and it was sweet!

The more water the vapor goes through the cooler the vapor.  But you only need so much as vapor is much cooler than smoke to begin with