I'm in the process of building both an MH-6 and an AH-6. I had many naughty words directed at DML for providing straight ammo belts that needed to be bent to reach the guns. I screwed up all four of the belts. Then I started rummaging through my various boxes of odds and ends and came up with a length of Tamiya M-3 halftrack track. I split the track down the middle and trimmed the edges smooth. Its flexible, serrated and just about the right width (although its a lot thicker than the ammo belt probably should be).
I fitted the guns tonight, and the belts look pretty good. I could have sprung for the Cobra belts, but hey, I'm cheap (although I did order the MELB kit from Cobra for the MH-6, per your suggestion, Grant....thanks mucho again for the help.)