Ok, got the transitions working. Still a little buggy, but usable.
On the start map, I have a non-moving elevator, and I've given the door and the elevator body props names, as well as global entity names. On the next map, I have a working elevator. The doors and body have the same names as the start map props, but no global entity names. I've got the trigger_levelchange as a cube above the elevators.
The buggy part, is that I seem to get stuck in the elevator when i get to the new map. Partly clipping in the elevator. I seem to get pushed out after a little bit, and I can kinda move myself out.
The placement of everything seems to be correct, equal distances and such. Any ideas?
Also, at the start of each map I have a portal gun spawned where the player is, but if the player comes from an earlier map, I'm not always in the right spot to pick it up again, so it'll drop to the floor. Anyway to prevent it from showing if its already equipped?