I ended up just following the instructions. Here's what I've put together so far regarding notes for corrections to the instructions. Someone a little more experienced at doing outdoor gear might not need it so lined out as I've done, but this is what I've been running into.
Maybe more info than you wanted.
Don't cut the tabs for the velcro. This is unnecessary. Don't sew the velcro to the WRONG side. They go on the RIGHT side. The instructions are wrong.
G4 Pack Addenda to Instructions:
HOOK AND LOOP
The instructions call for taking 3/4" H&L (hook-and-loop) and cutting it down the center to create a 3/8" wide pair. Cutting the 3/4" in half will cause it to unravel. I had this happen as I was trying to sew the cut edge. Also, having to sew within the hook area of the hook strip (which is unavoidable is you cut the strip down the middle) may be problematic for your sewing machine. I experienced cutting of the thread, bird nests, etc, while trying to sew the hook strips, and this problem was verified by experienced sewers on a usenet group. It is better to sew within the 1/8" border at the edges of the proper width strips. Sewing feet are available that will help facilitate this. Consider getting a contrasting color between the fabric and the H&L. Trying to sew black H&L on black material is not that easy when you're shooting for a 1/8" margin.
Supposedly there's some 3/8" sew-on H&L out there, but I could only find a reference for it on a UK website. Other references were for adhesive backed products.
You can buy 1/2" H&L strips for waist belt and shoulder straps from some place like www.owfinc.com or www.questoutfitters.com.
5/8" is readily available in retail sewing stores. I used this on a test shoulder strap and I don't see a problem right now, except it sticks out slightly. Another option would be to adapt the pattern to increase the seam allowance to 5/8" for the shoulder straps and waist belts, or at least at the place where the H&L goes.
If you do decide to use the 3/4" cut into 3/8" strips, here's two different tips I got on doing this:
1) seal the cut edge of the H&L over a flame.
2) Make small tack stitches to hold the H&L in place. Turn the fabric/H&L over to where the fabric is on top and sew from the back, using a zig zag stitch.
LAYOUT OF GROSGRAIN LOOPS AND H&L (HOOK-AND-LOOP)
Despite what the instructions say about cutting a slotted tab on the edge of the shoulder strap, this is not necessary. Also, the instructions are wrong where they tell you to sew the H&L on the WRONG side of the fabric. It should go on the RIGHT side.
[PHOTO OF PLACEMENT OF H&L AND GROSGRAIN LOOPS]
The instructions for laying out the grosgrain loops are almost non-existent. Diagrams would have helped. The pattern gives you a position for them, but little instruction on how to place them. For someone new to this endeavor, a little help was needed, which I got on the BackPackingLight.com site. But I only sought out help after I got a bit "creative" placing them myself.
If you're going to be sewing slick fabric, get a walking foot. This photo shows the difference of sewing a shoulder strap with a walking foot, and without.
[PHOTO OF STRAIGHT AND CURVY SHOULDER STRAPS]
[PHOTO OF WALKING FOOT]
Webbing for Shoulder straps
Watch it here, because the square piece of fabric needs to be folded TWICE, to make a smaller triangle. In the instructions, there are two diagrams showing to fold it twice, but it does not say the same in the written instructions. At first I only folded it once, and sewed it at an angle on the webbing. See photos.
[PHOTO OF FOLDED REINFORCEMENT]
DISCREPANCIES BETWEEN THE INSTRUCTIONS AND THE PATTERN
The instructions give positioning for the shoulder straps which differs from the lines sketched out on the pattern. The pattern shows them closer together, with corners touching, and higher up on the pack than the instructions.
[PHOTO OF PATTERN LAYOUT]
I called Quest Outfitters to get their feedback on this. They could not contact the person who developed the pattern or instructions, so they contacted someone who has made several G4 packs. The following is an excerpt from the email I got from Kay at Quest:
"...I just got a hold of someone who has made many of the G4's and she said the straps can be done one of two ways. If the person using the pack is on the smaller side the points of the straps should be touching each other (she is 5'2", 120 pounds and that is the way she does hers). If it is for a larger guy they should be separated like the instrucions say. She said there is no set in stone science to it."
4.4.2 Lashing loops go on top of mesh, not under.
Might be good to stipulate that when you trim the excess from the strap gusset, DO NOT cut the webbing. Even though the photo shows that, its a little confusing and I cut the webbing the first time through.
5.1 DO NOT sew all the lashing loops to the ripstop. Some of them should go over the mesh.
5.2 Specify that the wrong side of the mesh goes against the right side of the ripstop.
5.3 Might want to explain what you mean by double-stitch. I cannot find a definition for this anywhere on the web, except for crocheting. I just did two parallel lines of stitching.
Step 6.1 Specify that the wrong side of the mesh goes against the right side of the rip-stop.
The 1/2" opening at the bottom of the mesh sides, might want to explain what that's for.
If its for feeding out a hydration tube, 1/2 opening at the bottom of the mesh is probably not going to be enough to get a hydration tube through when the seam allowance is 1/2". Maybe an inch.
If its just to facilitate sewing it down to the ripstop at the corners, might want to say that.