There isn't a "proper" place for western riding.
The original style looked like this:
A more typical style for today is shown here. Notice the emphasis on a flexible lower back and moving WITH the horse:
Notice where the weight is distributed in a western saddle:
A significant amount of the weight bearing area is BEHIND the cantle. That is very different from an English tree:
For my purposes, I've decided to let my posture be driven by the saddle. For any saddle I'm in, I want my rump in the lowest part of the seat, and I want the stirrup straps/fenders to hang straight down. If that puts my heels under my hip, fine. I'm not going to force the stirrups back. If that puts my heels forward, that is OK too. I will move my legs forward or back for brief times, depending on what I'm doing or about to do.
Shoulder / hip / heel alignment is meant for dressage and western pleasure, both of which mean highly trained horses riding in an arena and covering the ground slowly, with lots of collection. That isn't the same as endurance riding, roping, etc.
FWIW, the British Cavalry wanted the back of the heel to be 1 inch in front of the chest. That was pretty typical in the US Cavalry as well. But a lot depends on what type saddle you ride, and I don't see much sense in fighting your saddle.