My husband and I are looking into doing this.When I was mulling over the same issues with the Nestera, I thought of one possible solution that might work. I didn’t purse it with the Nestera because of the way that the individual pieces hook together, but…
Depending on how your coop is assembled, could you with (1) replace a side with a wooden frame filled with hardware cloth, or (2) “raise the roof” by adding a similar frame, but this one going around the entire perimeter, sitting on the top of your walls and with the roof resting on top? This would be a band of ventilation, 6”-8”-10” high in the HWC screen area.
Either possibility raises all sorts of challenges like secure attachment and structural strength, but you would get a lot of ventilation in without cutting any holes.
Yesterday it hit 90 degrees, and it's not even peak summer yet. We had 5 very overheated chickens in our large Nestera. It's inside a run (and is fully shaded all day so I was shocked and dismayed that they were so uncomfortable in there) so I finally just opened the door and took the roof off the nesting box to give them more air flow. I think we are either going to see if we can build a roof extension to add more ventilation up top, or remove the back panel to add a hardware cloth panel for the summer months.