I disagree with the buzz about the lighter duty transport not being able to handle 1.5 mil tape, (1200' reels). Having done tune-ups on 388s several of times, I've found the reel/servo/motor section to have plenty of torque.
However, I'd not say the same thing about Fostex(es), as the 7" transports have belt driven reel hubs and not as sophisticated drive section,... a whole different story and another post, entirely.