do I need a special saddle pad for a english saddle?
I have what people tell me is an old army saddle or a spanish saddle and I'm thinking about getting a english saddle but I was woundering if I need to get a different saddle pad too? Also I think I know how the sizes work, for me (about 107lb) and my Paso Fino (15 hands) would need a 16 1/2" and size medium right?
If army saddle looks similar to english saddle you want you probably may use same pad. My guess would be it's different so yes, you will need english pad (either A/P or dressage depending on saddle) for english saddle.
I seem to remember that Paso Finos have a back that fits more like an Arabs's back. So, even though the horse is small, the withers are so-called "mutton withers". You might want to do some internet research on saddle fitting for Paso Finos before you assume it is a medium. Most Arabs need a wide or med-wide saddel to accomodate their low, wide withers. I am NO expert, just something I remember reading somewhere and I could be off on this.
Read, research before you buy . It sucks to buy off the internet and find it doesn't fit. Been there, done that.