Well, I had the opportunity to talk with Henry Shires as well as a few BPL staff members who all told me to steer clear of silnylon seconds for a number of reasons. That being said, I used SilNylon firsts (if that's the term). I did the "garden hose water test" to mine and no water got through any of the seems or anything. Water tight. According to everyone I talked to, the SilNylon seconds do not have the same waterproof abilities and will cause water to "mist" through the material. All in all, the whole thing was about 60 bucks total. All the fabric was purchased from thru-hiker.com. There are a few tips we discovered along the way:
1) instead of using pins to hold the fabric while sewing, we found a very cool water soluable "tape" like material that we used instead. WAY better and easier than using pins because it held the fabric together better without slipping at all. When finished sewing, the tape disolves completely with a little bit of water. No residue, nothing. It worked perfectly.
2) The 1/2 inch webbing for the pullouts is fine for the corner and side pullouts, but for the ridgeline pullouts, 3/4 or even 1 inch webbing works MUCH better; especially when installing the grommets.