I should go on to say I've found two ways to form a single loop, but neither is really good.

You can make a double loop as shown previously and pull one loop out through the center brummel. This yields a single loop, but there's a big twist in it. It's where the line is doubled, but my guess is that's still the breaking point.

You can also make a big locked brummel eye and then fold each tail back onto the loop for burial. That works well enough for flat braid, but is a bit bulky for hollow braid. It is also weaker than a straight bury because the tails have a sharp bend in them.

So far, my best (slimmest and strongest) solution is to take a couple of non-locking brummels, and then taper, bury, and stitch the ends (basically what liros shows in Pepin's link above).

Regards,
Eric