OK...I weighed my garage door, and purchased the appropriate springs
(same as the springs I had previously). The springs I got are 25X 42"
for my 64" door. This means the 'max stretch' for the springs is 42".

The starting point, from what I've read, is to attach the springs with
the door up such that they are taught but not being stretched at all.
I've done this. The next step in checking correct tension is to test
your ability to pull the door up and down manually with no issue. You
should be able to stop in the middle without the door going up or
down. I did this, and everything was fine.

So in the end, I look up at the springs with the door in closed
position, and I see they are stretched about 60"!! This is obviously
a bit over the 42" max, so I tried loosening the tension a bit. I was
able to do this somewhat, while still keeping the pulleys in position,
but this didn't change the stretch significantly. I tried going way
overboard and really undertensioning, but when I do that the pull
cables do not stay in the pulleys while the door is up.

So what's the deal? Am I misunderstanding max tension, or are my
springs setup incorrectly? I'm wondering if I need to move the
vertical mount point, or possibly change the way the other end of the
cable is secured (currently it connects to the horizontal track per
the instructions).

By the way, my old springs were stretched about this same distance,
and I assume they were the same rating.

Any help would be appreciated!

Jeff