Need to pour directly into the bear? Has anyone tried it? It definitely helps. What's going on with the bear?

In Ukraine, bears are few and only in the Carpathians in the mountains they live.

Interesting. And what are these cylinders?

Good job. And I made myself 15 liters, and removed the seat bag.

Я делаю вот так:

The most suitable width is 5cm for the whole triangle bag

Hi, I'm new to MYOG.  My first attempt at a top tube bag came out okay, but would be better with stiffer side panels.  I thought something like 1/8" closed cell foam sandwiched between 2 layers of fabric would work, but I'm having trouble finding the right material.  What do you use, and where do you get it?  Do you have any related tips you can share?  Thanks.

Use EVA foam. It is durable, does not absorb much water and keeps its shape. I'm talking to you as a bag manufacturer.

I make bags myself and I can tell you what is made of what. Ortlib makes pvc bags, it is welded with a hot air gun and glues very well, nothing cracks and the seams are very well sealed. Here are my works you can see https://www.instagram.com/bike_and_bags/ or on my website, for example, here on the trunk a bag looks like it is made of PVC https://bikeandbags.eu/work/velosumki-bagazhnik-20l/
The bags are also made of TPU coated with nylon or polyester, this material does not adhere well and is usually HF welded. Light bags are usually made of this material, but they are expensive.

And this is where bears walk so easily?

I am using pvc 620 density. Since there is no padding, seals, etc., the weight is more, but not much. Moreover, the bags are 100% waterproof. You can see my work on Instagram "Bike and Bags" Or here, but less https://bikeandbags.eu/foto-robit/

I am using Lokus. You can download third-party cards, at registration 3 cards are given free of charge, the rest are not expensive. You can upload your own. A very convenient application and very functional.

I have a bottle attached under the frame tube from the bottom and a drinking system comes from it, if necessary, I can put more water in a full bag. The half-frame bag is used when you need quick access to the water flasks so you don't have to take the hydrator.

An ordinary lock can be put on the rotor.
If I put on a chain or cable, then I reset the gears to a minimum, so that if they are cut off, then the thief could not go quickly.