So, im hung up a bit on a rules interaction set - I assume i'm making things more complicated than Intended...

movement difficulty : impassible terrain, "A unit cannot perform a standard move or a reverse during which it would overlap impassable terrain."

You're mixing different words - "moving over" something and "ending movement on" something with the base in full contact is different from "overlapping," which is to be placed only partially on something. So a speeder could not end balanced on the edge of a building or on top of a group of trees, but it can freely move over these things or end on a terrain with a flat enough top to be fully placed on it.

Sorry, I still don't fully understand...

It appears as if you're only talking about where the final position of the base ends up after a move... like this...

if there's a spot on a large piece of terrain where the base happens to fit in full contact, without overlapping, it's ok to ignore that it's impassable. And thusly if a double move would clear, but the single move causes a base overlap, you can't perform 2 move actions in that manner, as you can't legally stop after the first?

but - Impassable terrain flat out states Units cannot move through impassable terrain. Does the speeder keyword ignore that? or does cannot trump can?

Let's say there's a wall just under height 1 (As per high stone walls on page 9) - and it's impassable for repulsorlift vehicles, does speeder 1 let you move "across" the wall>?

According to the golden rules on page 4, effects on cards supersede the RRG, so the Speeder X keyword on the unit card takes precedence over the table in the rulebook saying that it's impassable terrain - so long as it is physically Height X or less.

On 5/21/2018 at 11:47 PM, Ravncat said:

And thusly if a double move would clear, but the single move causes a base overlap, you can't perform 2 move actions in that manner, as you can't legally stop after the first?

Correct, each action must fully resolve legally.

Speeder Keyword was in the RRG as well... I guess this means we could see a repulsorlift that isn't a speeder, in the future. It strikes me as odd as to how "impassable" is not really "impassable".

All keywords are in the RRG. In the Star Wars setting, there are many repulsor-based vehicles that aren't speeders (such as repulsor tanks, some of which have very cool models I'd like to see in Legion).

you also have to remember that Speeder is a key word which adds an instance, in this case ignoring terrain of certain heights, there will probably repulsor vehicles which won't have Speeder like hover tanks and those Imperial transports in Rebels