You might also play with a few different needles sizes and stitch lengths.
Sometimes if your stitch length is too tight you'll turn your garment into a connect-the-dots perforated piece of gear that will tear at the seam. The felled seam will help, but it can't hurt when your single stitch is just the right size.
As for the needles, I've found a new set that I really like. They are by Schmetz and are labeled "Microtex Sharp Needle". I use a #8 which might be too small for your silnylon but they also come in #9 and #10 sizes. What's different is the needle point has been flattened out giving it less of a profile as it punctures the fabric. I've noticed that since using the "sharp needles" the stitch holes are much smaller on average which I feel is a good thing.
As for thread, I'd give another bump for Gutterman 100% polyester plus a good coating of seam sealer or seam tape.