I think the flat braid is a good idea. High frequencies are a surface effect, more the better. I once had a customer that was building a computer room right next to a room full of high frequency generators putting out 20 KW each, growing germanium crystals. They directed us to ground the frames of all the High Freqency stuff with 2" wide copper braid, connected to a 4' x 8' sheet of galvanized steel buried outside. They always had interfenece problems in their old building. This installation was completely interference free.