Penile prosthesis : do you know if there is "oversize length" for afro-american race?

Onesize does not fit. Selection of prosthesis depends on the length of penis, one size does not fit all , not selected on racial basis.
Yes, but... The length of penile prosthesis is decided by real measurement during implanting surgery. But remember the girth and length of post-implant penis will be not as long or big as the original coming with life.