Well I had a try at rerigging the CatSaddle and I cannot say it was a success. On the other hand, I finally found where Smay hid the rigging for the stirrups, so rerigging the model is no longer a priority. Image below.
Here is the saddle and boot on unmorphed Harry. Someone else may manage to do a better job of it. The fit is not perfect, since cats are not shaped like horses. Obviously, one would need to scale the additional props in the set to fit the resized base items.
Somehow I've got all kinds of distortion in my viewport, but one can sort of see what I ended up with. (Now I think I'm going to have to see how this set fits on the House Cat.
The proportions I used were:
Saddle: 200%basic/x-axis an additional 103%/y-axis 94.4%
abdomen of saddle rigging: x-axis 110.2%/y-axis 98.5%
I also gave the x rotation a bend of 0.88
Boot: 200% basic/ x-axis 105%/ y-axis 95%
boot in boot rigging: x-axis 105.5%/ y-axis 93.4%/ z-axis 92.6%