Below is a diagram that illustrates the various tailoring techniques I've come across. I'm sorry the preview below is pretty crappy so you can look at the full size here.
However, if you are like me, and have the pear shaped body with a huge desk-job ass, having it narrower at the waist ultimately makes the whole thing look too small because it doesn't wrap around enough. Bah!! Time to lay off the ice-capps.
Mod Layout 2 looks more suitable for someone with a large belly.
I wish I knew the history surrounding these tailoring techniques but I haven't come across it yet in my research. Around what time did this become the standard way of doing things? I'll try to find out later.
But anyways, another technique to mention is in how the okumi extension panels are sewn on. Generally, one would assumed they are sew on straight up and down the length of the garment, but some yukata patterns show a slight curve near the top. By curve I mean the seam between the okumi and body panels starts to angle towards the shoulder after where the seam comes out from behind the obi (you catch that?). I believe this is only done on female yukata because this is claimed to balance the curviness of the female bust. It's so subtle that it's barely noticeable. I point an arrow to it in the picture below. Can you see it?
This is a diagram of an okumi panel with the seams marked out. The red arrow points to the seam that attaches to the body. I've circles the differences in seam allowance between the top and bottom.
But anyways, now that we have some context established, I'll be moving on to the sewing tutorials. Stay turned for part 5!