MY OPINION.
It is a good position, it has been used for xSeries, magnets, the older wedge Flexes like the FlexM1, the FlexDF etc
here is an example of a FlexDF installation I can think of in that position
As I mentioned above, the FlexM1 and FlexDF are the same form factor, and the FlexM1 you are considering, is more flexible than the newer Flex implants
see below.
FYI
The newer PCB Flex, like the FlexDF2,
has also been done, HOWEVER, the first versions of these had some issues with the chip seperating from the PCB slightly, causing failures.
A new design has been rigirously tested to eliminate /reduce the chance of this happening, BUT, I dont think the new design has been tested in vivo as yet, therefore not in that location yet.
All that to say, if you have the space to install, then I would see it as a viable option for you.
The skin there is a little thicker to get through so it will take some more force.
Ensure you go to AT LEAST the marking on the custom needle.
Good luck, keep us posted with your journey. ( there is actually very little documented installs there, so we would be happy to see yours )