Ditto on that... I never use an alignment tool on single clutches. Just eyeball them for center. Tried that on an easy pedal once. I wasn't long borrowing the alignment tool. It just doesn't work any other way on a twin disc type of setup.
I have use the transmission input shaft at times on tractor clutches if I have the shaft out. I do quite often change the front seals if I'm into one that hasn't been touched in a long time.