Board Thread:General Discussion/@comment-3083912-20140808154925/@comment-7472785-20140808204820

Well, it's safe to assume Penny is heavier than the average girl she looks...

Also we haven't seen Ruby carrying anything heavier than herself and Crescent Rose when she went full speed - safe the Nevermore she dragged up the cliff, but that may have been a shorter distance and we don't know to what extent the glyphs Weiss put as her running base helped her.