I’ve made one of my prints much more playable in the bottom notes by removing the string winding and sliding on a bit of bicycle innertube lubricated with petroleum jelly. This material is easier to work with than cork, and very easy to get: the bicyclist I asked wanted to know how many blown tubes I would take away.
I’ve now replaced all my wound joints with this bicycle innertube. The larger diameter tenons are spreading the tube out more, making it thinner, so I’m sneaking a bit of thread between the innertube and the tenon to give it just a little extra girth. It seems to me that this has fixed all the problems I was having.
This tube is marked “Continental Race 28 Light 18/25-622/630” The important number there I think is 18/25: that’s the tire width this tube works for. I advise trying to use a tube that’s somewhere between 18 and 25. (This is the French sizing, which is used in most, but not all, parts of the world.)
I’ve gotten good results when the joint takes a little bit of force to get together. People who’ve played instruments with cork joints will know the feel.
I’m still waiting for feedback from an actual flute player, so don’t go rush out and undo your lovely tenon wraps just yet. Ironically, the whole reason I was playing with bicycle innertube was an attempt to make a membrane check valve for my bagpipe blowtube: it wound up not being a good solution, but now my flutes play better 
I’ve got a hunch the reason the silk PLA was doing better is that was adding just a hair extra diameter to the tenons, making my wound joints just a bit more airtight.