Tom, at 5'11" you're about at a point where distance comfort would rule out most conventional channel jobs (maintaining floor at top of frame rail level). Generally it takes a guy 5'8" or less to be able to pull that off. There are variables such as how you're proportioned (e.g. short legs and long trunk), or what your tolerance for discomfort are. Trying to drive with your heels close to the same level as your butt can be hard on the back and hips.

Since you're on the glass body side of things, take a look at Gibbons, www.gibbonfiberglass.com , they have a design where the floors are dropped below the upper rail level to allow channeling and still have some seating comfort. Not only does this require putting "wells" in the floor pan (the easy part), but also a difference in the center X member of the frame (somewhat more difficult considering strength issues, but doable). Since they're in Darlington SC you might want to do a road trip to check out how they do it. Even if you don't like their product, the ideas can be transferred to others.