Howdy BondoBob..........not Elton here but, I am going to disagree a little bit with a couple of your suggestions. The outside stirrup leather / half double arrangement is very common on cowboy rigs, and does not pinch at all if done correctly. I have ridden them for many years, and I build a high % of them. Secondly, on the breast collar / martingale Ds........there are up high under the front buttons for a purpose........that is where they need to be. If a person is using a steer tripping type collar, then the lower position would be fine. There is no strength problem with the higher placement, as I am sure that Elton has the strings running through them, and/or has them screwed down to the tree.
Everyone sure does things differently, just my take on it.
Respectfully, JW