I try to avoid all positions in my hands due to climbing. The FlexSecure is placed in my left wrist, I never had issues with that position even when climbing larger cracks. Scanning it can be annoying at times due to its position, but thats no issue for me as I only use it with my phone and PC. I suppose if you angle your hand towards yourself, you could get a reasonably good contact with an EMV terminal.
If you go gym climbing only, placing a chip on top / side of your hand might be okay? Not sure. Depending on your style of crack climbing (tape / fist etc.) you might be okay, but it might be uncomfortable. I don’t think the chip would break though.
I definitely would not recommend finger positions for any kind of climbing.
Edit: Install Videos and Pictures 🩸 - #269 by StarGate01 (My implant location)