What is the rebound damping set at? That would affect how easy the shock moves more than how much air is in the body. The air would affect the ride height, though. I sit flat footed on mine, but the height is perfect for both the side stand and the center stand. Have you checked the linkage arms for loose or worn bushings? I don't believe your '87 would have the grease fittings from the factory, so maybe they are dry.