The Siegfried is a nice saddle but the only acceptable saddle is one that fits the horse. If the Siegfried is a good fit for the horse, that’s great. Hopefully the saddle fits you as well, since if it doesn’t fit you are going to fight it, it will put you in a bad position, and you’ll end up sore and on the ground. Probably both.
And a poorly fitting saddle WILL cripple your horse. The horse will be in increasing pain, you will cause nerve damage which may be permanent, and you will again, increase your chances of a serious accident.
There are some minor fitting issues that can be mitigated with a shim or a pad or a change in routine. Sometimes an asymmetrical horse can be helped with a small shim, which can allow the horse to continue working and to even out the asymmetry as he becomes more fit. But these are temporary things that crop up from time to time.
A saddle that fits well, but could use a bit of additional flocking or removal of flocking to customize it, can be performed by a saddle fitter, who comes out and performs the task onsite.
There are lots of good saddles/manufacturers out there. Stubben is one of them, but if the saddle doesn’t fit you or the horse it doesn’t matter how well it’s made. Especially for sports like eventing or foxhunting; any saddle fit problem is magnified. And if your horse gets sore, you’re going to have to hang up your spurs until he’s healed. There’s no other way except to stop riding and allow the animal to recover; and it could take months.