#1 Shoulder Carry - not with 18 lbs, but with 10 or less. I only do this once in a while, usually when my back gets soaked with persperation. Once it dries, I go to the standard method. Also, when grabbing a water bottle when walking. I can grab the bottle, but putting it back while walking is not easy. So I sling the pack on one shoulder and grab the bottle. It also is a good method to just change the position of the back for extended non-stap hiking. I suppose one could get use to it full time, but I am just more comfortable carrying it the conventional way. I travel a lot for business with a laptop, and tried a backpack, but for these short jaunts it is more comfortable carrying it on one shoulder. Consider Ray's suggestion as an option that might work for some people.
#2 Feet elevated probably only works for backsleepers. When I am really tired, I put my feet on my pack and start out on my back. It does help get to sleep and rejuvinate the legs. But once I fall asleep, I end up on my side and my body finds a level position automatically. If I sleep on the slightest incline, wheter head or feet up, my body ends up moving down the slope... not the slope's fault, that is just how my body functions during sleep.
Jardine has a lot of great information and techniques, but just go after those that make sense to you. No one has the perfect perscription on how to function in the backcountry.