Hey amal, have you considered designing dual tech implantables? With MIFARE DESFire setting the new standard, but HID Prox still being desired for universal compatibility this would be a very desirable chip to have.
I have a dual tech card (DESFIRE/Prox) and access to an X-Ray machine if it would be beneficial for you to have an X-Ray of the antenna layout.
Also, I make a pretty good guinea pig 
Nope. Dual frequency cards are just two completely separate tags stuffed into a single card. There are two separate antennas, and in most cases it’s also two separate chips also. Considering the space in an implant is extremely limited, I don’t see much benefit to spending a massive amount of engineering time and financial commitment to create a dual-freq implant when you can just implant two tags if you need dual frequency. Sure there is the small benefit of conserving space, but ultimately it would not be a good use of resources when there are so many other great things to put those resources toward.