If it were me, I'd cut the first two smaller amounts all from the
bottom. That should leave the top and bottom rail about the same
width so I don't think that would look too bad. The other two I'd
probaby have to take of each end. On the 6-1/2" cut you're going to
run out of rail at the bottom.

And the last two are regular doors, and they come with 6-3/4" bottom rails,
and 3-3/4" tops. So if I need to cut 6-1/2" total off one, (and 3-3/8" off
the other), I'm thinking that if I cut half of 6-1/2", or 3-1/4", obviously
I'd have almost no top rail left. But how much top to leave, out of 6-1/2"?
There is approx. twice as much bottom as top - so maybe 33 and 66 percent,
cut off the top, and bottom, respectively. That leaves
(1) 3-3/8" x .333 = 1-1/8", so 2-5/8" top, and 4-1/2" bottom left, AND
(2) 6-1/2" x .333 = 2-5/16", 1-7/16" top, and 2-7/16" bottom left.

I think this looks good on paper. Maybe I'll come back and try the first
and second too.

Thanks

This is all in the basement.