Well, the reasoning is twofold; one, since I have the Tommy Gate, a conventional shell is not going to work, and two, the whole reason I have the Tommy is to get heavy stuff into the bed. With a normal shell (even if I made something to seal around the gate), I'd be having to take it on and off which is a PITA.
I *think* these Can-Backs are fairly quick to put up and take down. So when we leave on a road trip somewhere, I can put it on and and least keep my gear dry until we get to the destination. I realize that security is zero however. I guess that is when I'll have to put my Queensland Healer back there. She'd take care of any intruders!
They (Can-Back) seem somewhat open to the idea of me dropping the truck off at their factory in CA for a couple of days while they make a custom rear piece to fit my gate. Although that is still up in the air...