I just completed my 11 foot pyramid tent (full post coming after I get back from Denali and the Kenai Peninsula in Alaska in mid-August). I installed a vent near the apex (a la MLD Supermid) and needed some sort of batten to hold the vent open. It had to be fairly stiff, pliable, light and on the soft side, about 14" long, and it had to deploy in a semi-circle. I considered metal, plastic, fiberglass, etc.
Finally a friend suggested using 1/4" poly tubing, the milky-white kind (not the really soft clear stuff). It worked perfectly, it is available in most hardware stores, and it costs next to nothing. I have no idea what MLD uses.
I will post pictures when I show off my new tent after returning from Alaska.