The height dimmensions are just a referance to go by to gauge if you have a properly purged shock. Basically, you start out by filling both sides so most air is purged through the comp adjuster. Then fill resevoir to top. Insert piston without introducing air, and push to bottom of resevoir. This will purge remaining air from adjuster. At this point the piston needs to be held down, so I assemble and use compressed air. If you have an extra hand or rig up a mechanical means that would work too, but be carefull not to scratch the inside of the resevoir. Now you insert the shaft assy, seal head toward clevis. While the piston is under the oil, tap on the clevis with a rubber mallet a few times to shock the shims open and release trapped air. You will see small bubbles, stop when they stop. Slide seal head toward piston, and slowly insert into shock body. Oil should be overflowing. There should be a tiny bleed hole over the oring, this is to release trapped air under the seal head. When the bubbles stop, push the seal head in to seal the oring. At this point the separator piston will want to rise from the oil displaced by the seal head, so it has to be able to move. Push the seal head down far enough and seat the snap ring, and pull back. The amount of separator piston travel in the resevoir at this point equals the amount of oil displaced by the volume the seal head over the oring, thats it.
This makes a real mess as your always working with a full and overflowing shock body. Just think out your setup before you start, like catch trays, etc. And trust me on this, the compressed air method for holding the piston is a lot easier and safer for the resevoir. One slip with a hard tool and the resevoir sealing surface is trashed.
I heard that a well known tuner at one time used to assemble shocks in a small fish tank of oil, to avoid the air problem.
