What are your tips for saddles and pads for downhill horses? I'm seeing more of them, so I guess we are breeding for it. I've ended up with one and don't really like the way anything fits him. 

I have two horses that are downhill (croup higher than withers with a drop behind the scapula).  One is more dramatic than the other.  With the one not too bad (he's 15.3 at the croup and 15.2 at the withers), I use a CSI pad with a Martin BTR with the 7" gullet.  For my other gelding (15.2 at the croup and between 15.0 and 15.1 at the wither) I use a CSI pad and a Double J Pro with the #10 tree.  As soon as I tried it, the dry spots and tail swishing went away.  He was obviously more comfortable.  Double J does make a #11 tree, but from what I understand, that is for REALLY downhill horses (greater than a 2" drop between croup and withers and a big drop behind the scapula). 

Bar angle is important too so you need to find a saddle with an angle that is "parallel" to your horses shoulder angle.  That makes a huge difference in fit, too. 

If you put a #10 tree on a straigher horse, it will make them sore.  If you can find someone that has one you can try, I would recommend that before buying one.

1st picture is the horse I use the BTR on. The 2nd picture is the gelding I use the Double J #10 on.

What saddle are you currently riding in? I believe that is the foundation and then get a pad to go with it. 

My current horse is 15.2 at the withers and hip. But she has very prominent withers so has the downhill looking back. Her sire is built as balanced and square as a quarter horse can be. His saddle fits her like a glove since the only difference between them is her slightly more prominant withers and the slight down sloped back. It's a Prorider, and I use a Five Star 3/4" pad with her. 

My rocket mare is 15.3 at the wither and 16.1 (almost, just a few hairs shy) at the hip. She would pin her ears when I put the Prorider on her. I had a Mike Green treed Frontier Futurity that fit her, along with a 7/8" Five Star pad.

Conversely, if I tried to put the FF on the stallion he would pin his ears. One saddle does NOT fit all! 

With the conformation of your horses it may be more a matter of padding the shoulders heavier to keep the saddle in place and not scooting forward. Neither of your horses have mutton withers or super duper high thoroughbred withers. They do have the downward sloping backs.