The Mopeka Pro Check LP tank sensors work well, but I think their attachment design is flawed:
1. LP tanks are curved on the bottom. The Pro Check sensor is flat. This results in a poor fitment of the sensor on the tank.
2. The magnets on the Pro Check sensor are not strong enough. They do not provide a secure sensor-to-tank connection -- especially since the flat sensor does not fit well on the curved tank.
This printable is curved to fit the bottom of an LP tank, has pockets for the sensor and stronger magnets. Secure the magnets in the pockets with a little superglue. I used these 1.25" diameter, 3/16" thick magnets from Amazon:
https://www.amazon.com/dp/B014Q4HNVO?ref=ppx_yo2ov_dt_b_fed_asin_title
The author marked this model as their own original creation.