what saddle for a pony

I am thinking of buying a pony to bring on, but am unsure if I can use my saddle on her. I know how to check the gullet etc but will an issabell werth be to big for a pony, as in will it take up too much of her back? She is 12hh and the saddle is a 17in.
Thanks in advance

That's one of those questions that's almost impossible to answer without seeing the actually saddle on the pony.... (and I don't know what an isabel werth looks like) but my guess is that it's going to be a little too big. You don't want to put too much pressure on the loin area or you will restrict movement and possibly cause pain. I worked with a 11.3 welsh/shetland pony for a while whose back was way too short for my 16.5 and 17 saddle so I ended up using a 15.5 from our school horse tack room. It was uncomfortable and pretty small for my petite self.... but fit the pony!

Unfortunately, I think a 17" saddle would be too big for this pony for two reasons:
1. It would extend too far down her back and put pressure on her loins. A big no-no as there are no ribs here to support the saddle and it can cause brusing. We have a 11.2 hand pony and my 17" saddle is too big for him.
2. Big saddles can have a tendency to slip forward on small ponies. But it really depends on the individual pony and saddle. This happened to me once- we were trying out a saddle on my first pony about six years ago and as I was trotting along, he suddenly put down his head to graze. The saddle slipped forward onto his wither and I somersaulted over his head! Lol I wasn't hurt and guess it would have looked pretty funny!

But yeah, it really depends on the individual pony. But I'd say probably not.

I have a 16" and a 17" that both fit my 13 hh pony. It all depends on the pony like the other 2 said. =]