I'm not surprised the Kentaur didn't fit - foam panel CCs rarely do, IME. And fitting with a pad? Saddle don't fit then, does it? Some 'fitters' drive me nuts
Although templating gives an accurate width it's quite rare to have a bespoke tree in terms of its shape. Not unheard of, though - I have an Ideal Grandee built on a cob tree (flatter profile than the standard tree). In most cases, given a reasonable match of tree to back profile it's the panel shaping which makes all the difference, and how it's flocked. That can mean changing the depth of the rear gusset, adding or altering the front or top-front gusset, deepening or re-shaping the panel across the diagonal (where the panel behind the knee pad turns at right-angles to run beneath the tree) or extending the panel depth down the sweat flap.
All these alterations are designed to help support the correct tree width where the horse is poorly developed (either naturally or artificially) behind the shoulder and along the top of the ribcage. Simply stuffing a standard panel to achieve the same clearance is not the method of choice because
(i) The flock often has to be quite hard to maintain support under a rider's weight and this won't encourage the horse to 'come up' under the saddle nor the back muscles to relax
(ii) The panel shape becomes more rounded, reducing the area in contact with the horse thus increasing the pressure per-square-inch in the saddle area
It sounds odd but it's true that soft flocking - over a larger area - can give the same (actually better in terms of comfort) support than harder flocking - in a small area. Of course the more panel on the horse's back the more its way of going will be affected BUT this always has to be balanced against practicalities. A horse you can't saddle is no real use.
A saddle fitted this way usually makes a real difference to the horse's comfort and way of going. Bear in mind a flocked saddle often needs a top-up after a short time (couple of weeks to a couple of months) as the wool settles, particularly on a horse with an awkward shape.
Hope that's useful info :)