I've made a variety of lids, and was wondering what the consensus was on non-rigid lids. Say foil, for example: it's too soft to be useful as a packing cover, and anything inside the pot could pierce it or wear it out. Are there two lids used? One for packing (plastic) and another for cooking? Or is a mesh bag simply enough to contain the pot and its contents, as the lid rides safely inside, folded or rolled? (This Q applies to soft silicone variety too.) In other words, is the use of a soft lid governed by packing technique?

Another dimension: how important is a tight fit on a lid? Obviously, too tight is NG, but soft lids often create gaps that let heat out compared to more precisely fitted lids. Issue or no issue?

Just trying to figure out which direction to go, thanks!

"how important is a tight fit on a lid? Obviously, too tight is NG, but soft lids often create gaps that let heat out compared to more precisely fitted lids. Issue or no issue?"

It kind of depends on what you have in the pot. I mostly boil water, so I like to see a tiny crack for steam to escape. Without that, I can't tell exactly what is happening inside the pot. Retaining most of the steam and heat is good.

If I go to high elevation, I've seen people trying to fit their lids to be steam-tight. They want it to serve as a pressure cooker. That will tend to cook food faster. It also takes a chance if it is fitting too tightly, and it could explode. Proper pressure cookers have a relief valve.

--B.G.--