I must admit to cheating somewhat...I wear those gel inserts in my boots; that uneven ground about killed my poor dogs the first Faire I ever went to. That was probably the first addition to my first kit!
I experienced some tightness in the shoulders, but not as much as it used to be, since I started using more than one belt- to redistribute some of the weight. I think I'm going to end up with a padded gambeson at some point, or folding hand towels and then tying them to my shoulders to help with the press-in of rings as the day goes on.
Oh, there is one problem area for me that I noticed no one else spoke on- wearing greaves. Since I don't have a full-leg harness, the greaves dig into the mask of the foot and can be quite painful if left unattended. What I did was get some bootstraps with a thick leather plate at the top that does help in mitigating some of that weight but I can still feel stress in my ankles due to the weight. What I think I'll do is go with a 3/4 leg harness that terminates into the boot like Sir Edward's and leave it at that. Maybe rivet some steel plates to the boot if I'm feeling adventurous (just an idea, small chance of that actually happening) - but I don't necessarily want to cobble it from my current greaves. I'll come up with something.
On another note, it sure would be nice to put that greathelm onto your saddle horn, wouldn't it, Sir Edward? God help them if they ever let us in on horses! lol