(I'm the original poster.)
"Close the door part way, and shove sticks (wood shingle,
of clapboard, or parts of a pallet) into the coils of the
Open the door all the way, and brace it. Move the springs.
Un-brace-the door, lower it, and take the sticks out."
That was the best idea I found. I did that, using nails as
the space holders, and it worked just fine. Adjustment
As an aside, all four springs already had the safety devices
inside them, so this was not as risky as some feared.
Thanks to all, and especially Goedjn, for the suggestions.