Hey Km
Im a little late to your question. the only thing about 1.5 clearance is that if you put anything kinda heavy they will bow temporarily. even then, if they are not touching the pipe, if you hit a bump they hit the pipe. same issue with supports. even though the bags look fine 'dry', they behave differently when loaded down. you can build some supports really cheaply (under $10) that can me made to fit any bag size.
viewtopic.php?f=1&t=2024
good luck and good riding.