Paul,
The first tank is an A.T.F. (all tubes forward). This type is easier to slide into a firewall cut out, or to slip into a tank compartment from behind (after drilling the appropriate holes through the firewall).
The second tank is the type to use on a profile, with too little nose room for normal tanks. I have to use that type on my Skyray 35, and will probably get a smaller one for the Acromaster, that is if I ever get around to building the Acromaster.

When is Nike going to loosen up some travel funds, so you can come back to Portland?
Bill