The screen should be pretty self explaining. (Sternus took the screen I stole it from the screenshot thread)
But yeah the odst drop bays were as far was I know at the underside or belly of the ships. So they should turn if its evne possible in sin.
It always kinda looked akward to see that shit coming from the front.
conclusion.
Only the ships that dont activly Bomvard the planet with front macs should be turned to face the planets surface with the underside.