fitting instructions basically say line up the marks, plus the usual headset gumpf
when i ordered i specced for 100mm headtube, asked about ability to use on other length headtubes
the answer was
The bearings are concentric with reference to an axis that is offset from the head tube axis.
If you move the cups along the head tube axis, the bearings will not stay concentric.
Hence you will not be able to run the steering tube through them and maintain the correct interface with the bearings.
Acceptable tolerance for HT length before you run into problems is +/- 1mm