Very informative post - nicely done.
I am coming from the first generation tacoma (95.5 -04) world, which is very similar to the current FJ front suspension, so this might be an appropriate time to share some previous experience with these types of spacers (which will
hopefully not applyto the FJ).
Some previous gen taco owners ran into two problems with spacer lifts that installed ABOVE the top plate of the strut assembly.
The first problem (for older tacomas) arises because when the suspension is fully compressed, there is a fixed minimum distance between the upper and lower mounting points for the shock which is reached when the bumps on the A-arm hit the stops on the frame. By adding a spacer ABOVE the top plate, it effectively reduces this minimum compressed distance by the thickness of the spacer. Some shocks may have a compressed length that is greater than this newly reduced distance, and as a result, and when the suspension is fully compressed, the bottoming forces are absorbed by the shock rather than by the bumpstops/frame.
The second problem (for older tacomas) arises because a spacer added above the top plate effectively increases the overall length of the shock assembly. This additional length translates into additional travel for the suspension, which in the case of the older tacomas, would result in additional stress on the tie rod ends, ball joints, and would allow the upper A-arm to hit the coil at full extension. All Pro had released a steel bolt-in spacer for tacomas that was notorious for this problem.
If anyone else does this mod (which I am also considering when I finally get my FJ) could you please do the following:
After you have compressed the spring and taken it off the shock, place the shock with spacer on top (but no spring) back into the suspension and jack the lower arm up to verify that the bumpstops are still the limiting factor in the compressed end of the suspension travel.
Hopefully the new FJ suspension is different enough from the old tacomas that this isn't even an issue, and I applaud the original poster for breaking new ground to install this kit. I hope I am not creating doubt or confusion over something that may not even be an issue. Thanks for sharing your install experience. I have done this so many times on my old tacoma that I have grown to HATE even the sight of a spring compressor.
Thanks,
Shawn