Good question. I used the pattern as-is the first time around, but as you point out, it got even smaller once I sewed and turned it. And I had my stitches inset only 1/4" from the edge. While I find the original handy, I made the pattern for my "stretched" version 2" wider. The size of the original is not such an issue with a gusset or weft added, but I'm happier with the larger version.
On the previous topic of liners, I've been using Barge too, my favorite rubber cement for the last 40 years even if it is getting harder to find.
I have talked to a couple of leatherworkers now who report delight with the waterbased cements recently available from Tandy (there are two of them, and I don't recall which they were talking about, if not both). They say it works as well as Barge without all the smell, plus it can be shipped without hazmat issues.
Oh heck. Long as I'm stretching this back to points about liners, I'll toss this in: I have the best luck with liners if I go to a little extra time and trouble. I follow normal instructions to let both the leather and the liner dry to the touch before joining them, but following that, I run a rolling pin with fair pressure over the joined pair to really force the bond. Following that, I let it set overnight before flexing. I've never had any separation after doing both, but I have had the liner bubble up here and there along any folds if I didn't. Just an FYI, and maybe not an issue with anyone more patient than I am.