How to decide frame perimeter on Rhino Treads?

We just got Rhino Treads for our robot, but we need to figure out the frame perimeter of them so we can make the center braces the correct length.

In the rule manual it says:

To determine the FRAME PERIMETER, wrap a piece of string around
the ROBOT at the BUMPER ZONE described in R22. The string
describes this polygon.

So would my frame perimeter be a string wrapped from the center of the front bumper and back bumper so that it will be diagonal?

Think about it like this: What would be the (outside) perimeter of the shadow cast by the robot if there is a light directly above it?

I haven’t been to a competition before, but are they actually going to wrap a string around the robot?

I would assemble the track units and put on whatever it is you are going to use for bumper brackets then figure out how long to make the supports for going across. Now keep in mind that with rhino drives you won’t end up with a square or rectangle… It will be a trapezoid.
We actually made ourselves pretty nervous the other evening and measured several times to make sure we were ok.

Not a string, a tape measure. Not a stiff metal one, but a flexible one made of plastic or cloth, like the ones used by tailors. Inspectors will wrap it around the robot with its bumpers removed. They will measure in the BUMPER ZONE defined in R22.

To Amplify a little bit. The frame perimeter is inside your bumper zone height wise. (4-12 in). Your entire robot must be inside the frame perimeter in starting configuration. Moving parts (Rhino tread, wheels) cannot be part of your frame perimeter.

You will want to make sure your frame angles up in the front along with the rhino treads in order to take full advantage of the clearance the treads give you. We are also using rhino treads this year and so far they have worked out great.
If you do angle it up in the front. Make sure your frame stays fully in the bumper zone (4 - 12 inches off the ground). In the manual, it only shows robots being measured from above as if they were a shadow.
I hope that made sense.

That is not to say that these treads cannot come within a millimeter or two of the frame perimeter, if you’re confident enough in the rigidity of your chassis that you aren’t going to be using your own bumpers as a brake.

Because the bumpers must be supported every 8" by (fixed, non-articulated) frame perimeter, you will need something fixed outboard of each tread, preferably extending slightly past both the forward and behind the ends of the treads, within the bumper zone.