No way I’ll implant anything there. I’m a barefooter, I like hiking, and I can’t count the number of times I’ve stepped on really rough stones and pebbles that don’t penetrate the skin, but deform it enough that anything underneath could certainly break. Even under the fat pads would be a significant risk I think - not to mention, good luck getting a needle to penetrate the hardened soles and thickened fat pads of someone who’s been walking barefoot for 20 years
I’ve decided to inject it on top of the foot, but at the lowest point to the ground, which is the webbing between the big toe and the second toe. That places it roughly 20mm above ground, which is plenty close enough for my long-range readers. And if I read it from above (reader under the rear bumper of my van) it won’t even have to be long range. Also, it’ll sit under both bones there, so it’ll be protected even if I hit something with the top of my foot, and it won’t become uncomfortable for the odd times when I do have to wear shoes.