This guide was originally found here, but given the site looks abandoned, I mirrored it.
Google translate from German: “Hello friends, I present this pedal jeep made of plywood, this is the one on the cover photo of the Popular Mechanics number that was published in November 2006. In some photos a small black box appears, it measures 5 x 5 cm. and they can use it as a reference for measurements. The map is in the first photos of the gallery. I hope you like it.”