Didn't purchase the kit. Next time I will just for simplicity sake. I just followed the instruction on the Ripstop by the Roll web site. They are very straight forward and fall into the following steps:
Measure pack and add 3 inches
I didn't seal the seams. The kids said they didn't have any problems. They encountered after noon thunder showers 3 of the 6 days on the trip. If you are in wetter weather you may consider sealing the seams.
I made a second cover with the membrane fabric. It is lighter and worked great as well.
Tip: Use clothes pins (the kind you hang laundry on the line with) to hold your layers of fabric together as you sew. We work to hard to keep our gear dry to ruin it with more holes