I doubt the layers of skin are thick enough to support an implant (unless you have a very leathery sack) and not a substantial backing.
I think this may be a better option
Infact, a while ago I suggested that it may be a good option for an xBT.
For fertility reasons, testie temperatute is important.
The xBT also has an anti-migration cap, so with the right placement, it should be comfortable and not move.
Maybe along the seam
Or the founding member [punny] of the “Flashy Sacky” club 
Or
blinky blue balls