His "technique" looks um...miserable for the girls and some questions

So they are now 4 months old tomorrow. The last 2 days our roo (Cochin) has been trying to mate. Well I thought it was attacks til I really saw up close this morning. It was funny really, like he was trying to surf or something. But he sure does get a beak full of feathers on the top of her head and back of the neck. Is that normal? Should I worry? He is going to be big and the girls are not. Also, now that he is doing this should I uncover the nest boxes and get them ready or do girls start laying on their own time? The boxes are covered cause they were sleeping in them. Oh yeah. One more thing....he is physically incapable of getting up on the high roost with the girls that I just put in a couple days ago. They love it. Maybe that is why they were sleeping in the boxes opposed to a roost just slightly taller than them. Is this going to create some pecking order/behavior issues?