Thanks for the link, Paulemar; it's what I needed. Also, I now realize that the video comes from the same place I bought my tiller.
Last year at this time, my Kubota L3940 and the Sicma (Phoenix) tiller were both new and I was working under the gun to get garden and field plots tilled and planted. The Eurocardan shaft was about 1/4" away from being fully compressed at its shortest working length. I snaked by, by extending both quick-hitch arms, (which bought me an extra 2+ inches of length), and then blocked their retreat with a big nut/bolt through each. It was risky, and I don't recommend doing this, but luckily, I didn't damage anything - and it got me by. This year, I'm not going to push my luck, so I'll be cutting the shaft down to the correct length.
After watching the 'how to' vid, the most valuable info (for me) was how to take the two required measurements: one is from the END of the tractor's PTO shaft to the (estimated) center of the lower 3-pt. arm hookup pins; the other is from the CENTER of the lock pin/capture bolt GROOVE in the attachment's shaft out to the (estimated) center of the hookup pins. (These measurements can be taken without the tiller being on.) Then add the two measurements together, and cut the PTO shaft down at least 2 inches LESS than that total. The telescoping driveshaft needs to separated, and both halves need to be cut, removing the same amount from each side.