The size of the recipient site does not stop an additional hair or two from exiting the scalp. This is shown often when what is believed to be a two hair follicular unit is placed and due to there being 1 or 2 hidden follicles 3 or 4 hairs grow in. I doubt that Propecia/Avodart will effect the number of hairs that grow from a follicular unit since those follicles are obtained from the permanent donor area.