I’ve read that the reason that DHT makes you go bald is due to sensitivity of the hair follicle to the DHT and not to too much or elevated DHT.
So a bald guy has just as much (thereabouts) DHT as you or I - its just that his follicles are more sensitive to it than we are - hence his hair falls out.
So I would suspect that bald guys have the same sort of penis sizes as those of us with hair… ie - the normal distribution…
See Ya,
BigJ