Since staring down the path of DIY and playing around with 1.1 and 1.9 oz ripstop, fraying edges have always bothered me. I have used a lighter which seals the for a while but if you handle the material much they start fraying again. I have not tried cutting with a soldering iron yet but it seems like it would be the same as a lighter.
I recently picked up a Singer 301a straight stitch (awesome machine) because I was afraid I would destroy my wife's sewing machine. One of the many attachments was a hemming foot. Today I started playing with it and I really like the result. It takes a little bit of practice to keep the material feed into the foot correctly. The results are an very professional finished look about 1/8" wide. Hopefully the pictures are viewable.