I don't know why anyone would purposefully choose to backpack heavy. It's so much more fun to go light, fast and far. I can see if it is for training, in which case, you can use containers of water. 2lbs per liter it adds up quick. The trick to making a heavy load more comfortable without a frame is to pack things very tight so nothing moves and keep the heaviest weight closest to the body. Some like the weight lower, others higher on the back. I suppose it depends on your center of gravity, although I'm not a scientist about these things so I can't say which is better for what. A waist belt can transfer some of the weight to your hips relieving some pressure on your shoulders.
If you really are wanting to go backpacking, go to Backpacking Light and learn how to make backpacking fun.
Ultralight Backpacking Forums @ BackpackingLight.com
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 180 x 2. Current Deadlift: 230 x 2