As some of you know, my primary hobby is building and driving radio-control cars and trucks. My primary area of interest is a highly specialized type of vehicle known as rock crawlers, which as the name implies, drive very slowly over rocks.

In competitions, the truck bodies, which are made of vacuum-formed Lexan, are allowed to be trimmed to 70% of their original size, to allow for tire clearance, etc.

The question is, how does one measure something as irregularly shaped as a truck body to an exact spec, in the field? The difference between a 70% trim and a 71% trim could constitute enough of a competitive edge to disallow a truck in a competition, so precision is necessary for the measurement. Speed is also an issue, with 40 or 50 trucks to measure a tech inspector could be all day on body detail.

The bodies are painted with different kinds of paint, and more or less paint affects the weight of the body. Therefore, simply weighing a pristine body (as I proposed) and using that as a baseline leaves plenty of room for error. A competitor could run an "illegal" body with a couple of stickers to make legal weight.

The weight itself is not the issue. The issue is having a body that still has an intact cab and fenders, but allows the wheels to travel without rubbing. This is the "spirit" of the rule. Many competitors cut the doors off halfway down so the body will not get snagged on the ground, and thus does not look like a truck anymore, at least not one that's above water.

Defining the 70% rule has been the subject of much debate here:
but we are still a good ways from a definitive answer.

I thought I would tap some of your keen and penetrating minds, since you like to measure things. Let's see how you do with an irregularly-shaped three-dimensional object.
Original Post

Are bodies expensive?

At a contest each contestant could bring an original unmodified body, identical to the one that was modified, before it was modified.

Modified body can't be altered in any way except by cutting. No stickers, no paint.

Weigh the two to determine whether the 70 percent has been adhered to.
Typical bodies run about \$30-35. The high-demand discontinued bodies are both hard to get and expensive (\$70 and up when you can find them).

When new, the bodies are clear, and they are painted from the inside.

It's somewhat pointless to use a clear body, as the rule is there to ensure that the trucks look like trucks. With clear bodies they'd look like ghosts. Perhaps I should have made that clear (ha ha) in the first post.

Although, if each competitor were to document his body's weight during the buildup, 70% could be easily determined. Not everyone has a precision scale, however, but this is probably the best solution. I see no other way to measure the body besides weight, given the irregularity of the shapes.

A database with the weight of the commonly-used bodies is in the works.
How about a body weight range for each range of wheelbase? This doesn't address what to do about excessively heavy paint layers though.
That might work if there were anything uniform about the bodies, but there are so many variables (length, width, height, material thickness, depth of detail relief, paint thickness) that a uniform measurement is nearly impossible.

One solution that just occurred to me is to have the builder save all the scraps from trimming the body, and weigh those, too.