I installed guards several weeks ago after getting my Rocket. I used my lift to staighten the bike vertically, not to lift the bike or engine.....then I used the small scissor jack from my car under the very front bottom edge of the engine block, I put a small board between the block and the jack. I raised the jack just a couple turns to take pressure off the long engine mounting bolt. When the bolt turned fairly easily then it was easy to drive it out with a long screwdriver.
PS I am sure I learned this method from someone on the forum but can't remember who it is.