this is looking really nice! I like the big roof overhangs
Me too! I wish I had made mine overhang that far.
If you haven't started making your nest box yet, you might want to consider this one. The front hinges down, instead of the roof hinging up, so no worry about leaks.
And, what I like best about it, is when you want to clean bedding out of the box, you just scrape it right out. You don't have to scoop it. I made mine from these plans, and they were very easy to follow:
http://www.thegardencoop.com/blog/2011/03/10/external-nest-box-plans/ That site expects that you are retro-fitting their nest box onto their own coop design, but it can be fitted to any type of coop construction. (So their first step of removing the walls and framing the opening, might not be necessary.)
And speaking of weather stripping, I actually put some around the door of my nest box to stop cold drafts in the winter, but you probably won't need to worry about that. Looking at how the foam sticks and squishes down, it does seem like it would stop water leaks. It's pretty cheap stuff, so it wouldn't be a big loss if it didn't work. I have seen other people asking about how to stop the hinge of the nest box lid from leaking, so if you search around the forum, you might come up with what worked for them.