What was the reasoning behind specifying the width of the beams and the width of the test base? Neither would seem to have any impact on how teams prepare for the event, so as far as I can tell it just establishes a hoop for supervisors to jump through. I can't use angle iron, for example, and running the event on a lab bench might well be out of spec. Is there some way that these measurements might affect competitors that I haven't thought of?
Primarily to help the novice event supervisor who wouldn't know where to start or to think through all the aspects of it. If you look at the draft rules from last year, we specified a standard 8' table and 2x4s. We abstracted that out a bit to provide more flexibility by talking about beams and surfaces (which is where the general dimension came from).
The easiest route is to just get 2 metal 2x studs and a standard classroom table. If we just specified a width of the track, some novice event supervisors would like use thin pieces of wood, which will bend and warp. Likewise, many lab bench tops are too narrow to both have the track and standard iron support stands for the lasers / photogates.
Angle iron is going to be a lot more expensive, but in reality is probably an acceptable solution if you want to use it. As event supervisor you have some discretion and can notify the teams in advance about such a minor tweak. As long as you have the same conditions for all teams you should be fine.