I made mine from some 1.3 sil I had leftover from making a new tarp. My wife had a peasant dress that I used as a basic model (in terms of proportions relative to my size). I left the bottom hem open so that I could deal with the waist & fit. Once I had it hitched up to were I felt comfortable, then I started on the length.
I knew I'd want the length below my knees, but not down around my ankles. I walked around a bit, put a foot up on a bench to mimic climbing, etc, till I was happy with the length, coverage & flexibility.
Total weight is 1.8oz. I use a 10oz pullover Torrentshell for the top, so my rain gear is 12oz. I know other solutions like a poncho or Driducks are lighter, but I like the fit & utility of my gear, especially since I use the TS as a windshirt along with an R1 top.