So after switching my hot water over to a heat pump, I really don’t need to ship in 48kg bottles anymore, which means I no longer have to wait for a delivery. 19kg bottles are tall enough to reach the hoses, and easy enough to handle and transport. So I will be moving to 19kg bottles as soon as the last 48kg is empty.
I will probably make a square carrier out of angle iron, probably some 40x40x3 should be fine, and fit this with hinges onto another similar construction, with the load cell on the unhinged side.
I will have to check the math, but intuitively I would think that since it is now supported at three points (two hinges and the load cell), the support itself is triangular, and if you put the bottle smack in the middle, the load cell will get one third of the downward force. So even a 20kg sensor can handle a total of 60kg load and give better resolution.
All that remains then is to protect the load cell, and since it is really an electronic strain gauge and I merely want to protect it from dripping water coming from above, I might get away with mounting an upside down enclosure to the “weigh bed” with the load cell inside the enclosure. A hole in the lid of the enclosure should be okay and whatever is needed to connect to the outside world can go through that. It will probably attract a little insect traffic though, will have to see.