From your description and the photo it looks quite secure. My only thought is to make sure the people door can't be pushed or pulled open. Also watch that your birds don't decide to roost in the pen at night. Birds can get close enough to the sides of the pen to be grabbed and ripped through...
I will admit that my idea of "secure" has changed drastically from when I first built my coop and run. Is your coop surrounded by a hardware cloth apron to prevent digging predators? If there is a way into the run predators will find it. Once inside the run, an open pop door is practically an...