Tim,
If you have access (paid member of) to the MeTime website, look at the gallery for the Fall Nats for last year. Look at the 20 ( B) hydro class photos taken during the heats. You will see a number of variable ways we put a cowl on the NR styled engines.
BTW, consider putting the pipe on the port side (left) of the hull. It offsets the weight of the rudder and the turn fin on the right and gives better balance to the boat. Mine is always on the left. If you have noted, Kentley and Preston run theirs on the left side. They are world record holders and they do things for a very good reason.
John