Dutch: I can not find it. I was reading in an arborist tree climbing form that 5 passes thru the rope (like 2 S's in series) was an acceptable way to spice in the field. It was tested to be the same as a locked brummell and a fid bury.
Dutch, I am in a similiar predicament as you. This past weekend I made my first bridge hammock. With all the measuring, cutting and sewing. I accidently forget to sew in my rings at the four corners. After spending most of the day at the project. There was no way that I was going to rip the ends apart to put in the rings. After much head scratching the solution I came up with was to. Insert my 7/64 amsteel suspension lines through a 2 inch pieces of clear vinyl tubing. Then inserted that through my corner loops. And then I spliced a locked brummel eye. The other end of the line was tied to the ring at the peak of my suspension triangle. I'm using 3/4 PVC pipe with wood dowels inserted as my suspension bars for now. The vinyl covered loops work just fine with this set up. Perhaps something similiar to this could work for you.
PB that is what I am doing only I just want the locked brummel so I can detach the suspension tiangle via 4 Dutch Biners. I was able to make the brummel and then bury each end in teh brummel. I didn't test it yet but it looks like it will work. However I have to do it next time with the tubing and on the hammock which should make it interesting. Then I have to do it 8 times because I have 2 to do.
I use soft shackles on things that I rarely need to (but sometimes do) need to detach. I use Dutch Biners for ease of connecting and disconnecting with verve, style and elan. Mollified yet?
One type of soft shackle that you should invent for this application is the type that Opie made with a bury instead of two strands. It is shown here. Pay attention to the stopper knot, though. It's supposedly not as secure as a lanyard knot, but easier to tie. This type is more trouble than most to fasten and unfasten, which is why it makes a good connecting point for a Dutch Biner. It's basically a loop with a lump in it (the knot).