I currently have 10 birds in there.
5x7 is not large enough for 10 even before you add 7 more. It's only enough for 8, and that's tight.
The Usual Guidelines
For each adult, standard-sized hen you need:
- 4 square feet in the coop (.37 square meters)
- 10 square feet in the run (.93 square meters),
- 1 linear foot of roost (.3 meters),
- 1/4 of a nest box,
- And 1 square foot (.09 square meters) of permanent, 24/7/365 ventilation, preferably located over the birds' heads when they're sitting on the roost.
- 68 square feet in the coop -- 8x8 or 6x12
- 170 square feet in the run -- about 12x14
- 17 linear feet of roost
- 17 square feet of ventilation -- except that my experience in a climate not quite as hot as yours is that I should double the ventilation space or even triple it UNLESS the coop is located in deep shade.
- 4-5 nest boxes.
Combining coop and run into an Open Air coop is an excellent option in a hot climate.
This is mine: https://www.backyardchickens.com/threads/large-open-air-coop-in-central-nc.1443812/
And some others:
https://www.backyardchickens.com/articles/jens-hens-a-southern-texas-coop.75707/
https://www.backyardchickens.com/articles/my-positive-local-action-coop.72804/
https://www.backyardchickens.com/articles/california-living.68130/