If you have a bridging saddle and the saddle no longer bridges
when sat in, regardless of the tree size or shape, the ends will come
toward the middle as weight is applied. When the weight is lifted the
ends of the saddle will go away from the middle. This back and
forth movement works on the wither and loin area.
*I am not sure why you are assuming the saddle
would be bridging If you begin
the fit with a tree that does fit the back,
then it is not bridging.
With Reactor Panel, unlike many other saddle
designs, you can see the actual bottom
of the tree and place it on the bare back of
the horse to check fit. Many saddles have
so much padding or flocking you cannot
really determine the shape of the tree inside.
