Will the flange on this kit adhere to nylon and other surfaces?
I honestly do not know the answer to that question. If you try it, please let me know and I will post your comments here.

Can I order just the flange or just the brass insert?
The flange can be found by clicking here. The insert can be found by clicking here.

Why does the vacuum bag have to stay connected to the vacuum press after full vacuum is achieved?
Yes because a perfect seal on a vacuum bag is virtually impossible. Here are some things to consider.

• Sometimes the bag closure doesn't seat perfectly across the opening.
• Sometimes the bag stretch a bit after full vacuum is created and will then need a bit of additional vacuum. This happens most often when there is a large project in the bag. You'll hear the vacuum system cycle off (if you have any auto-cycling system) and then turn on again for a few seconds. After that, it may not cycle again for several minutes or even hours.
• After many uses some bags develop pin holes which can be almost invisible. In those cases, it's best to let the vacuum press keep the bag vacuum under control.

If the vacuum system is disconnected from the bag, you won't know if there is a leak because there is no vacuum gauge on the bag itself. If the bag is connected to a vacuum press system, you can easily see the vacuum level by looking at the gauge on the vacuum press. The vacuum inside the system is the same amount of vacuum inside the bag. If your vacuum press cycles on and off too frequently during a project pressing, you'll know there is a leak and if you can fix it. However if you can't fix the leak, at least the vacuum system will keep manage the vacuum in the bag until the panel is finished.