Haha, well riding for hours and hours and even weeks on trail rides, I guess I don't think about posture when I ride, which is why when I seen yours (which I believe is good) I figured you rode english because they concentrate on their posture. I personally, not really slump, but I don't sit up to to straight, I let me shoulders relax. I guess when I ride, I am just sitting up there, not thinking of a care in the world except that we are in the middle of nowhere riding, lol, so I guess I am not the best person in the world to talk to about posture, haha. But you do look good on Romeo.
I do want to comment on one thing though and it was the 4th picture down that caught my eye on it. I would say your feet are too far forward in your stirrups. When I ride I just use the balls of my feet on the stirrub, not my heel and not the curve part of my foot. You just don't want to be caught with a foot stuck in a stirrup if something for some odd reason were to ever happen. ;)