This is one for the experts. Which capship/big freighter has been known to enter the atmosphere of a planet in the films/EU, and which has been described as being able to land?

Is there a hard and fast rule I should apply (silhouette 6+ cannot land?)

Emergency landings like in Episode III show that ships of a certain size may break apart when they enter the atmosphere, as they were never meant to do so. I'm looking for the best ship to evacuate a planet. It has to have a favorable cost/passenger ratio, and landing capability.

(Hoth has been evacuated by GR-75s, which are cheap and carry a 100 passengers each. The CSS-1 star shuttle is a great, albeit slightly more pricey alternative. Both have landed in the films. So far, these are the ships to beat.)

Ships don't have to have FFG stats, but I would prefer ships from The Clone Wars or Rebels or the Movies (mostly because I'm a sucker for gorgeous 3D renderings at the gaming table.)

Thank you guys so much!

Rebels shows us that Imperial Star Destroyers can enter atmosphere and hover at fairly low altitude. It doesn't show them landing.

I would think taking an old Trade Federation ship out of mothballs would give you a great deal of room to evacuate people.

Good point. You could use smaller landing craft to ferry people to the cap ship. Hmm.

During the Clone wars they used these to drop troops and equipment from orbit or upper atmosphere:

http://starwars.wikia.com/wiki/Low_Altitude_Assault_Transport

However, these assault ships could land and drop a huge ramp for walkers and clone battalions:

http://starwars.wikia.com/wiki/Acclamator_I-class_assault_ship

Check out the Ryloth series on TCW...

Great! Now, if I want to convert storerooms into makeshift quarters to get more passenger capability, how would you mod the starship?

I think for a planetary evacuation I would not mod the ship. Evacuations like this are normally last minute and bare bones. Regardless of political affiliation when Katrina was bearing down on New Orleans they used anything they could get their hands on to get out of town including school buses. In Star Trek (yes they may be the enemy) TNG the Enterprise is sent to evacuate people from a planet. With all the resources of the Federation they do not send a specialized ship just a big one with plenty of cargo bay to hold people so they can get them to safety.

Maybe put rows of cots in the cargo bays and a food line in one of them so it can feel like the are refugees.

Edit: Another show that has a great refugee atmosphere is the new Battle Star Galactica series.

Cots are bulky compared to mats on the floor or hanging hammocks from cargo tie down points.

In Star Trek (yes they may be the enemy)

Star Trek (TOS): Green Women, Princesses, space battles, evil empires, heroes that solve problems with blaster/fisticuff diplomacy, a focus on wibbly-wobbly science.

Star Wars (4-6): Green Women, Princesses, space battles, The Evil Empire, heroes that solve problems with blaster/lazersword diploamcy, a focus on hokey religion.