Here’s a great and fast way to help determine what your stretch webs should look like. Some folks have been doing this for many decades and others have never heard of it. I can assure you, most people are very skeptical the first time they hear it, but I can also assure you that it works great! Unfortunately there are only one or two places in the country I am aware of that you can buy it, but fortunately it is extremely inexpensive so you can buy a bunch of it. I purchased dozens of 8″ x 12″ sheets of various thicknesses a couple years ago and it was only about $150 total.
The wax has a light adhesive on one side of it and it is relatively transparent. So you simply print out your best guess of what you want the stretch web to look like and then peel back the adhesive paper and place it on the paper printout of the stretch web. Then, take an X-ACTO knife and carefully cut around the pattern, being careful not to nick the wax, which of course would cause it to fail prematurely. The cover of an old plastic 3 ring binder works great for a cutting surface. (The width of the web isn’t really critical that it is extremely precise because what you’re really looking for is the “length of line” when stretched.)
If the wax doesn’t break when you stretch it to the same place (X, Y and Z) that the actual strip will stretch, then the strip most certainly will not break. In the last picture below, you can see if you look closely that the wax looks like it is close to breaking, but that’s because it’s been stretched a number of times already. It doesn’t have the durability of steel!