Weight inside a backpack has no brains.
Some one loading up a back pack with 150lbs of weight would also be brainless. So don't attempt to create a 10 step program for yourself out of this.
Try one like this:
Get a rider on the back with you and ride around a local parking lot until comfortable.
Then another day take it to the streets, like around the block a few times.
Next, do a small trip, like to a burger joint and back.
Plan something further next.
Soon having a pass. will become second nature. If it's the passenger you plan to ride with the most and he/she isn't experienced, then they will most likely benefit by learning something from this too.
Ohh I'm thinking you might want that shock on 3 for your two up situation. Any one else can agree or disagree, but this is where I'd have it for your senario. Like I said I'm around the same weight and I keep it at 2 while 1UP