Some rough calculations for Ogre length, assuming a cube to model ratio of 2.5 (estimated by sloppy clay model, but the ratio is usually 1.75-3 for chubby things) and a density of carbon fiber, 1.55. I think tanks have a density of around 1, with most other vehicles being below, towards 0.1, mainly due to crew and cargo pockets (AI Ogres might be more solid, but overboard density might make them sink).
nyrath