Pullet-Shut automatic coop door . . .

[cmarlowdrive]

Does anyone have this door? I was wondering if I can install this door over the existing hole in wall or does it have to be exact to size? It looks like this door just installs on top of the existing hole on outside wall. The hole in my coop does not match the dimensions of the coops listed, mine is smaller. Does this door leak when it rains?
We are working on our coop a little at a time and have the hole cut out but trying to decide what door we need to install.

Any thoughts are appreciated, pros and cons . . .