There’s a natural hollow there between the bones, but behind the knuckles. It’s about as protected as you’re gonna get.
Of course if you’re aiming for sensing only, then you may wanna wait for round 2 of the Titan run. It should be a much much more sensitve sensing magnet.
No dice for that location already have several x series in my knuckles and Amal and others have said you should leave several inches between magnets and x series lest they migrate