The scale for this image may be a little off. I tabulated circular orbit velocities for most of the current bodies at 100km, and here's what I got: Tylo- 2009m/s Kerbin- 2248 Mun-466 Minmus- 105 Moho- 837 Eve- 3196 Duna- 847 Ike-284 Laythe- 1808 Vall- 720 Bop-122 Given that orbital velocity at 100km is related to each world's gravitational parameter, this gives us a way to guesstimate each world's radius- assuming density is constant. Problem is, I've forgotten the formula!!