[EricH]

A couple things to consider...
gondorf, you underestimate PVC's bendability. It won't break with a ball hitting it. If it does, someone is probably penalized for exceeding the muzzle velocity.

Wetzel, <G16> says that any robot extending a blocking device (over 5 ft tall) in front of the center goal will be DQ'd. Plain enough, except that the flag is an exception to the height limit. So, the only question here is: Is the flag a blocking device? I predict that Q&A will have to think this over for a while after someone submits the question. (And by the way, you will be penalized if the top of the flag is over 6 feet from the floor, according to the rules.)