First, welcome to the Parrot Forums!
I am assuming that you are considering Breeding the two pair of Yellow-Naped Amazons. I hope that they are both proven Breeding Pairs, which means they have produced eggs that where hatched and Weaned several sets prior to your purchasing them. Just placing young Amazon pairs together offers no assurance that they will Breed!
A couple of recommendations:
First, very impressed with the overall design and your commitment in building these large outside cage structures.
Second, it appears that you have chosen to build the cage structure itself from Galvanized metal. The type of coated metal is created by dipping metal (commonly steel) into hot molten Zinc. Zinc is classified as a heavy metal and Parrots are know to chew on the structure and ingest the Zinc. This can result in Toxic Zinc Sickness, which can be fatal. If you elect to use this type of cage structure, you will need to yearly have your Parrots checked for the presents of Zinc and treat accordingly, if found!
Third, does the shelter have floor drains, if not, you will want to consider adding them to your design.
Forth, strongly consider adding a double door system that allows a space between the outer door and the inner door. This will greatly reduce the likelihood of your Parrots flying out while you are trying to get into the structure.
Fifth, it would be a good idea to provide some level of separation between the two units that will block the view of each unit. It could be very possible that the males will spend excessive time at the separation defending their unit and hen. Take great care in how you construct this separation (limited, to no sight) since you already have a solid back wall. With only two open walls, you 'could' have limited air flow depending on the wind direction on any given day.
Our resident Amazon Breeding Expert has been busy of late, but may see your Thread and make additional comments.
It is highly recommended that you use Natural hard wood tree branches for perches. Target branches that are at least 2" (50 mm) in diameter and larger for Yellow-Naped Amazons. Do not use dowels. Choose branches still part of the tree. Do not use fallen dead branches. Remove the bark and wash, rise and let dry in the Sun!