WV, hey I am sure you know what you are doing, but...
I did just that, in a 1.9 oz DIY double layer in ripstop. I hand sewed pretty much like you did. Excessive movement (and possibly having the hammock hung too tight) caused the bottom layer to tear out in a line along the stitches. Could have been a few reasons, including poor alignment, stitches too tight, what have you, but it seemed fine till I tryed to get the sleeping bag comfortable and jerk it up towards my shoulders... now I am nervous about any stitching in the body of a hammock.
An emergency of my own making...is still an emergency.