Dave,
perfect documented! I never have done this job, but anyway a question/idea:
It should be possible to release the tension of both springs without using compressors.
1. To loosen the both bolts of the bottom plate (not the central nut!)
2. To put a jack (in a secure way) under the lower central nut/bottom plate and lift slightly
3. Step by step loosening the upper kingpin bolt and at the same time lowering the jack till the tension is released.
Assembling in a reverse way.
Looks simple and reliable (no use of compressors and threaded rods), but there might be some obstacles, as I did not try this method.
Peter