When you say rump to withers you mean stand at the back and take a picture to the front not from the side? She isn't a particularly down hill horse but is very wide with a round barrel. Every saddle I have put on slides side to side no matter what you do.
This is her without the saddle, it makes her look almost up hill which she definately isn't
This is more acurate but hard to see because her head is turned
Here is the saddle on my horse with no pad
sorry this one refuses to go smaller and rotate maybe someone else can fix it...
With the riser pad
Sitting the way the white pad sits on its own
Pushed up into the gullet
Is the riser supposed to go lower than than?