Adding: You said you ride in a western saddle, so I am assuming the problem here is different meanings to the word "collection". I mean it in a dressage sense - a horse that is working off the leg and seat of the rider, from the hind end, back into the rider. I don't know much about western collection.
Riding with collection in a western saddle should be the same concept as collection in an english saddle or whatever kind of saddle you have. Good riding is good riding. The only difference I can see would be possibly the conformation of the horse you are riding.
As I said before, you sound very knowledgable on the subject so I am sure you are aware that conformational differences can make it easier or harder for a horse to get under himself and drive from the hind end.
I essentally ride a mare who was bred for cow work. She has a huge hip and, as I said in my other post, built kind of "tucked under". It makes it easy for her to do the reining type moves of sliding to a stop, rapid back up, roll backs, fence work, spins etc. When she takes off, you gotta hang on or you'll be left behind
I guess, due to that conformation, when watching us, my trainer noted that she already traveled very correctly, driving with the hind end under her, but was not soft in the face. So that is what we worked on, me driving from behind while asking for the softness in the front. I can assure you, my legs and seat feel it when we work on collection, certianly not my arms or hands.....that would be horrible.
When you say that a horse should naturally soften in his face when driven forward, that confuses me a bit. How can they soften if they have not been taught to give to the bit with a basic give and release method? You have no idea (or maybe you do) how many horses I see that are not broke in the face and neck, meaning, they have no lateral control, let alone vertical control. Forget collection, they are a danger to the rider because if you get into trouble with them, they won't give laterally so you can get them under control. It a
Is a "hole"in training that I see all too often that is covered up with the use of big bits and other equipment to try to keep them under control. Therefore, I never assume a horse has that skill unless I see it or feel it for myself.
Giving to the bit is a basic skill that all horses should have and I guess I started with that in my original post because for me, even though it has been years since I taught her, that was the starting point of softness. It was by no means the end. My horse learned to give the five basic body parts early on too....1 & 2 -atlas and axis.... the lateral and vertical head and neck flexion 3-shoulders 4-mid body & 5-hindquarters.
I guess my thought is that you are coming from a more advanced perspective, assuming that the horse in question already has those traits under his belt, while I was kind of going back to early training because I see so many people aiming for collection on horses that are not truly broke through the body yet. They put draw reins, training forks, running matingales, huge bits, all in the name of getting a "headset" like you were talking about, and we both know that is wrong. My point was that to start, make sure your horse is truly broke and soft in the face. I guess I should have added body too, in retrospect. If he isn't go back to basics, or you won't be acheiving true collection when you do start asking him to drive from behind.
Whew.....this really is hard to explain.