A western saddle can and usually will extend on to the loin: All western saddles extend over the loin Saddle fit - Western compared to English Part 2 Saddle fit - Western compared to English Part 3
One English saddle I used had a too narrow channel and put too much pressure near the spine. It showed up by the mare getting very sensitive to mounting and dismounting. My Australian-style one - which I got with a very American horn - didn't cause a problem. I did get a few bruises where the Mickey Mouse ears (poleys) slammed into my thigh when she would spin (we did a lot of that for a long time). But that was good, because it kept my hips aligned with my horse in a spin, and that probably kept me on her many times when I would have come off without them. While I really like the Australian stock saddles, not everyone does. My wife and daughter both hate them
. There are also some very cheap, badly made Aussie imitation saddles on the market.:
I eventually drifted west. I'd avoid a "slick seat" saddle. Bought one, and ended up adding sheepskin because the slick was just too darn slick. "Butt on Ice
" is not what you want to feel on a spooky horse:
You could try a rough-out saddle in western. I think that gives a more secure feeling than a deeper seat.
This was taken years ago when my mare was on the verge of spooking. There was a large moving van outside the picture, with men moving around inside, and she was very light on the front end and thinking about spinning and running - or a "Turn & Burn"! Notice I had one hand on the saddle horn. If my horse is threatening to spin hard, and on pavement, I throw pride away and plan on staying on. A firm grip on a saddle horn made it easier for me to keep my shoulders over my hip (and thus over the horse) in a hard spin. In the end, in this case, she finally decided to prance past it, stepping high, snorting, and giving it the evil eye:
You might look up some YouTube videos of cutting horses. A cutting horse reminds me of a spooking horse, repeated again and again and again. If anyone knows about staying on a horse who reacts hard, it ought to be a cutter! Good luck!