Something I only remembered a hour or so back. Sorry
The 325 ships lead by The Alien Pirate Admiral who is The Imperium's first encounter with his race is worth 624 Fighting Dice and 18 Capital Ships by Imperial classifications(according to Drinax part 10), but only 436 Fighting Dice and 1 Capital Ship by his Races classifications. Does that effect anything?
Discuss the Traveller RPG and its many settings
"Bigger is better!" Actually the bigger something is, after a while it just becomes a bunch of meaningless numbers. One can build a ringworld or a Dyson Sphere, but your characters are only going to play on a very small part of it! All that extra land area that your characters never see doesn't add much at all. One can go the other direction too, and confine the Imperium to our Solar System. The Solar System is a big place and can easily hold 11,000 Worlds with the same population as the Third Imperium. There would be no need for a Jump Drive either. The main thing to consider is that most of these 11,000 worlds would be artificial except for Earth, Luna, Io, Europa, Ganymede, Calisto, Titan, Mars, Venus, and Mercury. Everything else would use spin gravity and have an artificial environment. That said, there would be no reason to make an environment that was not friendly to humans. Atmospheres would tend to be Thin, Standard, or Dense, with the majority of them standard.