I started by perusing any material I could find on the subject by searching the forums and web. I got a lot of good information from my friend, Eric Wilson as well as some old C&F forum posts. I experimented with a few of my own methods which worked out extremely well. For example, one of the things I noticed when looking at pictures of vinyl bags others had made was that the seam would get a wavy look to it due to the unpredictability of the glue spreading in multiple directions when the bag is clamped. What I ended up doing was: I laid my bead of glue around one half the bag and then gently folded the other side over and maneuvered it until I was satisfied with how the cut edges met up. I applied gentle pressure only to ensure that it wouldn't move too much on me I then used the spine of a DVD case to sort of squeegie the glue towards the outer seam (away from the inner bag) so that it would encourage the glue to spread outwards rather than inwards. It seemed to work very well.
The bag is laid on top of the Tim Britton bag for comparison. Keep in mind, the vinyl bag has a 1" (approx) glue seam so the inner bag dimensions are even smaller than seen here. I made my measurements based on this template and added 1" all around to allow space for the glue to spread without intruding on the desired inner bag dimensions. (I made two lines, one was the inner bag target dimension and the other was the cut line which was 1" out from that. The glue bead was laid between the two lines, but closer to the inner line and then smoothed/pushed outwards with the dvd case after the sides were together)
This shows a close-up of my tie-in method:
Rather than go with the star pattern cut, which tends to rip very easily with the vinyl when stretching over the stocks, I used round cuts. The round, continuous cut preserves the integrity of the hole and doesn't create any weak points for the material to tear through. The vinyl stretches quite a bit so the cut hole size was less than half the diameter of the stocks. Air tightness has been achieved on all three stocks. If I could give advice to someone on the way to the store to purchase the fabric, DO NOT let the clerk fold it (you can see the unsightly fold lines in my photo) because it makes the vinyl harder to work with and also results in creases in the material. This could be a big problem if the crease ended up in the neck and encouraged it to kink on you, otherwise it's merely cosmentic.
Here's the set put together:
