Oh, thanks for the info btw
Hehe...well, it's info. Whether it's useful to anyone....
In my numbers up above, the "tiny" magnet is the one I ordered from kjmagnetics. The "rare earth" one is the donut magnet (with the hole for a screw) that came from tselectronics.com.
If you're installing in such a way that the magnet and sensor will almost touch...then those tiny magnets are great! You can either surface glue it, or drill a very shallow hole and make it flush mount. But in cases where there might be a gap between the sensor and the magnet, those tiny ones don't reach very far. In those instances, that little donut magnet reaches as far as the regular 3/4" deep magnet, but will require barely much deeper of a hole to reside in as the tiny magnets.
From what I can tell so far, my sensors for the bottom sash will require a small gap between magnet and sensor. Since that gap is more than 1/8", that means the tiny magnets won't work for me. But those donut magnets can reach plenty far with their magnetic pull.