Do you mean two colors of the warp. If so I haven’t done one because Rebecca at UBraidIt has a good one. You can pick it up on RU-vid. Look for UBraidIt channel.
Hummmm. You would need multiple hooks to secure the buckles. Then you would need to divide the warps between the two. Since there’s an odd number of warps I’m not entirely sure how to do that. I’m afraid that I don’t know anyone who does English style girths. It would have to be something that I’d have to experiment with.
Hummmmm...Probably about 39'. That's end of buckle to end of buckle = 26". You need 47' for a 32" cinch. Of course, the amount varies from person to person depending on how tight you warp it up. I like to error on the long side as you can't piece on another piece.