Steve, I agree with you, the visibility may not be as good as a front seat, but if building a tandem Cozy or side-by-side "whatever" conventional airplane were the two options, I would build the tandem Cozy in a heart beat.
For what deronjthomas wants to do, a tandem Cozy would be within limits of the current Cozy compared to "something else", 60" wide. Even if he were to change the turtleback, get some engineering help and do it.
That would not stop him from designing, building and testing (the first time). If that were the case we would all be sitting in the grass wondering what it would be like to fly...instead we get to watch people like Mike Melville corkscrew into outer space. I'll say it again design, build, test whatever it is.
I guess what I'm saying is don't let anything stop you. If you want to do something, educate yourself and do it. It is that easy. (Easier said than done, I know.)