In the Highland Model 3, enrolling the keycard in the forearm is quite difficult (or maybe impossible). Even in P3, where mine is located, it was challenging to enroll. Luckily, after enrollment, you can scan on the door, and it will still allow you to drive—until you get out, at which point you’ll need to scan the door again.
Model 3:
The Cybertruck looks like it would be equally, if not more, difficult to enroll if implanted in the forearm. I’d recommend enrolling it prior to implantation just in case. In a worst-case scenario, you may be able to use a repeater sticker or press your forearm forcefully against the center console to get the perfect angle, allowing enrollment while implanted in the forearm.
Cybertruck:
I recommend P3 over the forearm for reasons beyond just Tesla compatibility—it’s simply easier to present to any type of reader in any orientation. If you’re concerned it might interfere with Muay Thai, you can always stick to the forearm, enroll it prior to implantation, and hope that, if you ever need to re-enroll post-installation, a combination of repeater stickers and creative arm angling would work.
I don’t know the exact coil placement of the Cybertruck, so it’s possible enrollment in the forearm would be easy. But based on my Model 3 experience, I can’t guarantee that getting a read in the forearm would be reliable (in the center console for enrollment, the door is easy to read in damn near any location).
Overall, no regrets going with P3—I’d do it again.