Funny to see this thread: I'm right now in the process of removing some 8 feet or so of rubber hose some ran to a trans cooler, and replacing almost all of it with hard line. Short hoses at ends to connect to trans for easier R&I, and at cooler end. With fittings, not hose-clamped to the hard lines, I hate that.
Normally I'd run 'em alongside the pan rail, but on this car there's no room to get there, so they'll run along the left frame rail.