I don't think that stuff really weigh that much does it? How did the bike react when or if you had a passenger on the back without the tour pack? did you say you changed the length of the rear shocks? maybe read that wrong. I am thinking that is extreme cases the front end would become lighter but not do what you are describing.

2007 Speedmaster and miss it! 2013 T-Bird Storm and Luvin it! Catching a yellow jacket in your shirt at 70 mph can double your vocabulary