has anyone had experience installing a dog door into a cross-panel design storm door? good or bad.

 

Welcome to the forums! The main problem I see is what you will do with the main door closed. Having the dog door in the storm door won't do you any good, and will defeat the purpose. Dog doors are usually placed in walls or doors that won't be covered by a storm door.
If the storm door is a stand alone, then you can cut the aluminum at the bottom, build a frame to fit the opening, and install the door within this frame. The aluminum alone won't support the door for very long.

 

An added thought, if the dog can come and go, so can every other critter that discovers the door.

 

True.. and I guess that's the 'risk' us pet parents have to take..but in all the years we've owned dogs..and using the 'dog door' (which is installed thru a wall), we've never had any other 'uninvited' guests use it....-fortunately.

 

We had a cat door on the kitchen door where we used to live. Once in the middle of the night I went in the kitchen and there was a coon sitting on the kitchen table calmly eating grapes out of the fruit bowl. He finished his snack, hissed at me, hopped down and slowly waddled out the door. No big hurry.
Another time I noticed "slug trails" on the kitchen floor near the catfood dish. I finally caught one of those big timber slugs as he headed for the door at full speed. He had been coming in every night and eating leftover cat food, then going back outside.

A dog would probably keep visitors away. Cats don't care.

You'll probably have visitors if you have a pet door. You just may not catch them.