External or internal laying boxes in tractor.

[Zahboo]

I am doing a tractor kind of like a playhouse coop. It's 5x3 and the coop is 2x3. It's just for two bantam girls. I will have their feeder and waterer hanging below the coop, and inside there is only a roost and nestbox. I was looking today and was thinking if I should do a internal or external nestbox. Internal is of course easier, but I need real opinions

 

[Zahboo]

Okay, here it is. I don't know if the nest box will throw it off, it looks a little weird. 1' square with a little incline to shed rain that drips off the roof. My girls use a 8x8 right now, so it's big enough.