Probably a number of corvette-sized transports... I doubt they'll actually land, but more likely that they have numerous transport docks. A small group (5?) of the large transports can probably carry about 100,000 soldiers. Remember how much "used space" is involved in dedicated warships... so much space for weapons, armor, and supplies. A large transport could carry a barebone compliment of weaponry, poorly armored, and supplied for short treks to nearby systems. I don't see 2,500 Elysium transports that big of a deal--the US Navy's actual sea-going crew is much less then the US Army's land-going crew. Remember that we (the US) put half a million soldiers into Iraq alone--not to mention the number in Afghanistan.