Outboard jets recommends a jet tunnel, which is considerably smaller than a normal tunnel.
http://outboardjets.com/boat-selection/
Ideally a tunnel 9-12" wide and 1-2ft long is preferred, and a mod vee will help dissipate bubbles from the intake, and turn a little tighter. I dont think I will find a mod-vee jet tunnel, and will likely end up with a flat bottom jet tunnel. I want the foot above the bottom of the boat. I may research float pods on a jet tunnel