The screws on the bottom attach the ridiculous servo mount at the bottom. I'm thinking the top and bottom had to be cut in different areas and maybe some of the vertical stuff on either side of the servo had to be sacrificed to make this work, or at least to make room to get a Dremel in there. It's hard to figure out, but it appears some of the shortening was done just ahead of the rear suspension and some under the servo, which would explain the missing vertical pieces and the stupid big servo mount.

Dammit. I'm bored and I've got a spare chassis. This is a tempting puzzle.

EDIT: I need sleep...and a life. Okay, figured out the chop. Not that hard to do. Not quite as sanitary as this one, but very, very close.

Also, in the video, the track boards look exactly like those at Tamiya events. Coincidental? Yes. It was shot at http://genkikkosan.com/ . They're a shop with a smallish room that's primarily for mini 4wd, but they do run m chassis sometimes.