Have found the approach that suits me best, but it is quite difficult to put into words. Will try, anyway.
The result will be much better than any stuff sack you can buy. Sorry I don't have pix.
First, use sil on 1.5 or 1.9 oz fabric. The heavier weight about eliminates the sewing issues with the 1.1 oz.sil. More important, the slightly heavier bags are much more robust, and way easier to stuff. The weight penalty is very small. 1.9 oz sil is available form Seattle Fabrics and Warmlite. If you find a quality sil coated 1.5 oz, pls. post the source because many will buy for tent floors.
Next, the dia. of the bag must be enough so that when you make a tube of a rectangle by sewing a flat fel seam, you can get the whole seam through the sewing maching. Don't try a flat fel seam with skinny tent pole bags. The size of the rectangle will determine the size of the bag, except that you must oversize at least an inch on two opposite sides to allow for the flat fel seam, at least two inches on one side to allow for the cord sleeve, and at least three inches on the remaining side of the rectangle to allow for removal as described below of fabric at the closed end of the bag.
If one side of the fabic is more coated, sew the flat fel tube seam with that side out. Or don't, but then turn the tube inside out before continuing. Before sewing the tube, at one end of the rectangle, fold over, hem and sew down two opposite square corners by forming small triangles, so that when the tube is sewn, there will be a V shaped cut of maybe 2 inches at one end. This is so that when you hem that end of the tube, there will be an opening in the ends of the hem sleeve for the cord that closes the bag. I double fold all my hems so that there are no exposed raw fabric edges, and melt the edges of all cuts before sewing.
Next, flatten the tube and stitch closed the other end.
Fold the raw edges and stitch again so no raw edge is exposed. There are several ways to do this - use your imagination. I shave one edge so that the other will fold over it and stitch the fold.
Now create two triangles by folding the closed end of the tube to create a square-shaped end with the stitched seam running between the centers of the bases of each triangle. Stitch at the fold lines to make the square end permanent, and cut off the triangle shaped pieces about 1/2 inch outside the seams. I also fold and restitch these cut edges to eliminate the exposed raw edges.
Then seam seal the work at all seams and when dry, turn the bag right side out. Create the cord sleeve by sewing a large hem at the open end of the bag. Insert the cord of your choice with a bodkin and install the cordlock of your choice - I like the "B" (ball shaped) locks.
Done. BTW, although the closed end of the bag is square, it won't look that way when stuffed.