Buck pen info

So I bought my fencing and post gate and have laid out a 40x75 paddock on grass for my Nigerian dwarfs when I get them. In my search I h posted and got plenty of response and found a doe kid and one buck that is just too pretty to pass up. The owner wanted to keep and was going to in he wasn't sold intact since he was from good bloodlines and was so unique. I had not planned on getting a buck whethered or intacted but like the breeder said he's just too good to pass up and now I have a month to build my pen before they are ready according to her he will be fine in the pen til about a year before hell start to apply his cologne for the ladies.
So what size pen does a buck need? I will have extra fence left over to build a small pen even could split the pen I have some but want to keep him a little away from the girls so he is less likely to get all dolled up lol but I don't want to create a huge pen. how close is too close? I would like to keep him within eye sight but have the chicken pen between my chickens free range a good bit so hell have company but if needed I can always get a whether down the road.
So im asking size of pen suggestions for a dwarf and how far away from the does is enough?