Are imperial forces coming from beneath the ship in ANH ? They come from a main door I think ? (I’ve found some Tantive IV blue prints but it’s not that clear actually)
We don’t get to see Organa’s ship in Rogue One, so there is no real evidence that Leai’s ship isn’t Organa’s ship 19 years later (the Falcon has changed between ROTS - Solo - ANH, why wouldn’t the Tantive IV ?)
I always presumed a docking tube was attached from above. Or the side? One of the later sound mixes adds scraping sounds in the moments before they blow the hatch.
Also possible they just pressurize the bay with a force field, the way they do on the Death Star, and just climb onto the hull. My old Kenner Star Destroyer has a little sliding hatch, (retracted in this photo on the right) and the novel has one closing after the Tantive is captured.
