My rig sounds very similar to idaho_h20's... but it's a 15' Sotar SL (very similar to the zephyr). I have tons of photos on this site of my frame. Also WWMW double rail (older versions) with MDO and a bunch of NRS parts as well... and some speed rail fittings and some custom fabbed stuff (front fishing seat and rear seat/floor supports).
I like the 15' for fishing - more space between casters, floats high and is still easy enough to row.
here's a couple to help illustrate:
I do not like how any of the big names put together their rear frames...but love this system I came up with a few years ago - easy ingress/egress and gives a solid floor for the rear fisherman or a great suspended place to stack gear on an overnight.
This is how I originally built it... now I use speedrail fittings but same basic idea.