I've seen this question here and elsewhere, and in fact, I asked it once myself on another forum. The answer I got was good, but it was incomplete. After playing with the settings for a while, I finally figured out how to do this.
Terra gets its colonist supply from two sources: the initial amount of fuel ore on hand and the regeneration rate. The number of colonists has nothing to do with any other setting that I've tried, and I played with it for quite a while. The amount of ore on the planet will be the number of colonists on the planet. Since Terra is based on an Earth planet type, it only holds a maximum of 100,000 ore. You can make a new planet type to hold up to 10,000,000 ore. However, just making a new planet type and setting a high level of fuel ore won't do the job. When you go into Terra, you still get the 100,000 colonist limit. I finally found out how to get around this.
1) Go into the Gold editor, option (2) and make a new planet type (option "+"), based on the Earth planet. If you like, you can change the name, under option (A).
2) Under (1) Maximum values set (F) "Storage value for Fuel Ore" to 10,000,000.
3) Under (4) Miscellaneous, set (D) "General Deployment" to "No" so your players can't make this planet. Set (F) "Planet is Active" to "Yes".
4) Save your settings.
5) Go into (N) "Planet Editor" and choose an unused planet number. I recommend one up near the top end of planets allowed so it doesn't take up a space that players would use for a player planet.
6) Set this planet to the same type as the type you just created. Y
7) Now under (B) "Ore OnHand" set that to 10,000,000. Do not make this planet active.
Exit to the main menu.
9) Go back to (N) "Planet Editor" and choose "1" for Terra.
10) Under (B) "Ore OnHand" you may now set this to any number up to the maximum of 10,000,000. That's how many colonists Terra will start out with.
11) Exit to the main menu.
12) Under (G) "General Editor One", option (H) "Terran Colonist Reproduction Rate" set that to any number you like up to the maximum of 65,535. That's how many colonists Terra will regenerate in 24 hours.
I don't know why steps 5, 6, and 7 need to be done, but if I don't do them, Terra won't hold over 100,000 ore. If there's an easier way, I'd like to know how it's done.
fury