Janet Gale's chicken coop

My husband built this wonderful coop for our 6 new chicks. My sister
named it Palais de Poulet (which is chicken palace in french). He did the
design and measurements in his head, sizing it so the metal roof pieces
all fit without having to cut them. We live in the northwest near Mt.
Hood. We get a lot of rain, some snow, and have 6 wild wolf dogs (one is
feral we can not touch), with lots of other predators around, so we wanted
to provide them with as much protection as possible: electric fencing and
a big covered porch.
We insulated the walls but not the ceiling. We have an electrical outlet
for a heat lamp and heated water bowl in the winter.
We used 3 screen door (springed) hinges for the chicken door. We have a
pulley system that goes from the chicken door to the front door so we
don't have to go in the yard to close them in. It's not as secure as a
latch, but hopefully it will do the trick.
He built them some roosts out in their pen which they really like. They
are tacked up against the post in the middle that holds up the bird net.
We made a few mistakes we still need to fix: We didn't slope the top of
the feeder so they sometimes roost on it.
He built this fancy poop chute which we haven't tried yet, except he
trimmed it with one by four which will be a barrier for sweeping it out.
My friend had a good suggestion to replace it with sloped floor molding.
We made the nest boxes 12"x12" instead of 16"X16". We don't know if they
are too small for them to use, maybe not?
Another question we have: We don't know what to use to line the boxes. We
use the pellets on the (vinyl) floor, but they don't seem very comfy for
the nest boxes. Someone said we shouldn't use straw because it is a good
home for mites.
We would like to build them a bigger yard, but aren't sure how we will
arrange it or if we should try to build them a tractor instead. I'm still
looking for good tractor examples. Can tractors be made dog proof?
Let me know if you want me to send any other photos.
Thanks again for the site!