So this has been haunting me for weeks. I have to say it.
in those early modern medical texts that Carlisle read, the key to successful conception was thought to be the casting of the 'seed' when the woman reached her orgasm, so a penis that was too big to cause potential pain for the woman was often thought to be one of the reasons of infertility. So this poor guy probably just looked down at his huge di*k and muttered "Slud! I might not be able to procreate".