Size - I honestly don't know. There are claims on the internet this is about Mars/Jupiter (expansion) or Saturn (contraction) or ruler of the 8th aspected by Jupiter/Saturn but I don't believe this. Astrophysiology in terms of qualities like this are very complicated when something is in the sphere of normal.
Deformities etc. - Major genital deformities are often associated with the angles on terrible degrees, 8th House planet or Mars being in a bad place in combination with those terrible angles, especially when combust by the Sun. Saturn can give a meaning of castration in very rare situations like these.