Many thanks everyone.
As to size I estimate the following:
pack volume 1242 cu in (20.4 liters)
collar volume 293 cu in (4.8 liters)
2 side pockets 180 cu in (2.9 liters)
back pocket 137 cu in (2.2 liters)
total volume 1851 cu in (30.3 liters)
Yes I used coated silnylon for all pieces.
As to pattern, most of it was drawn as I went. The only pattern pieces needed are the curve bottom. The ion was big help here. The ion shape really is a thing of beauty as I began to study it. The back is straight down, has a 90 turn then curves and tapers to the front. My pack is similar.
As I describe the panels I added 1/2" seam allowance to all seams. Generally this means each pattern peice is 1" larger than describe for 2 seams.
The back panel is 23" long by 11" wide. It continues on another 9" long to form the bottom. The continued portion though tapers to 7 inches. It is tapered because the front panel is narrower then the back. The front panel is 19" long by 7" wide. The ion panel has a slight hour glass shape to it, mine does not.
The pockets are 4" wider than the panel it sits on, next time I will add an inch to both. The side pockets are 10" high and the back pocket is 13" high. The bottom 4" of all pockets is mesh. The pockets use shock cord to make an elastic edge. The shock cord from the front pocket continues to the side of the pack and is run through line locs making it easy to add tension to the sides.
The collar is 13" high. To stiffen the opening I used 3/4" gros grain. To close the pack you simply fold over the gros grain "band" several times and snap the buckle. This adds more top compression then I find in most draw cord packs.
Hope this helps.
Jamie