Actually, BlkBird, I DL'd the picture of the BME Xtreme off the BME site, kept resizing the file until the distance between the centers of the exhaust ports matched the center-center distance shown in the "in cowl tuned muffler" diagram in the "Gallery" section of the site, then cut out the "flanges" from the printout and made my flanges that size.

The dimensions are:

c-c of bolt holes. . .1 7/16"

Flange hole (square with radiused corners) 13/16" x 15/16".

That will be just a tad oversized on the hole, and line up the shape with the bolt holes. I use 1/8" thick washers with a 3/4" inside hole for my flanges, then remove the unnecessary material with a grinder. The headers are then brazed.

Hope this helps.