I thought the shock spacer simply returned the up & down part of the shock to its normal range. Not sure how they make for more down travel then normal. Good to know about the CV boots rubbing.Their downside are many - they extend the suspension down travel, which makes the OEM upper front control arms contact the shock at max droop. Also, the front CV boots will rub the spacers if the wheel is turned and the suspension is slack. The extra rear travel is stopped when the sway bar hits the rear strut bodies, and the extra travel leaves the rear springs really close to falling out. You also need to bend the brake line brackets or get extended brakes lines for the rear as the extra travel is more than the slack in the line.
On the rear reading up on the install of rear shocks it seems a lot of extra pressure is needed up on one end & down on the other end to remove the coil. Can wheeling really reproduce this & cause the shock to fall off. Also I don't think the rear shock spacer adds any space to the rear spring area that holds the shock. The install instructions I've read on the rear never mentions needing extended brake lines. Just to be careful as you manually compress one side it pulls on the brake lines.