I've been having fun making double locked brummels but it seems like the downside is that you need access to both ends of the whole line where as if you just feed the amsteel back into itself and stitch it you don't.
I however really don't like the lack of eloquence on having to stitch the loop.
I came up with something I'm guessing already exists and I want to know what its called so I can find out more.
Pull the end of line through itself completely like you do for a locked brummel.
Then using some tricky wire work feed the end of the loop into itself, around the inside of the loop and then back out and down the inside of the main line.
It seems to work but ends up compressing the amsteel so that the loop you end up with is a loop of bunched up amsteel. I have no idea what the load capacity is.
If this is too confusing let me know and I'll snap some pics.
I used this rather than a back splice to dress the dangly bits of my UCR's so if I need to add weight I've got a loop already.