Wouldn't the safety concerns have been the same when the larger door was need for the other dog?... Just a thought...

Regarding a solution, I have not seen any factory "down-sizing" kits for such an application. Certainly something can be done, it will likely just require some ingenuity to build this in. Completely custom. The quality of the finished product will be determined by the skill of the installer, although I have to say, that fact that you alluded to the door being a high end product worries me slightly about cobbling something together.

Bigger dog, larger woofing. Smaller dog is just love bug, and no woofing. This is a odd size door, not really custom, just something that stores would have to order from the mill, I guess. If any one out there has any ideas, please let me know. A picture would be great.

+1. Surely it can be done but I am not certain that it won't look worse than just the larger door.

Check with the people at Pet Doors USA, a good company that's been around for ages. (I have no connection, just as a customer for 25+ years). Call and ask. There may be some insert-within-petdoor or some such.

Thanks much for all the advise. If anyone else would know of an idea please post.

I’m in a similar situation what’d you end up doing and how’d it hold up?