Tranny questions?

Things I would try, in order of easiest to hardest;
Maybe tighten up the band some.
A little more line pressure might do it.
And a stiffer spring in the accumulator.
One of the higher ratio apply arms could help.Anything over 4.0 really. The higher the better, but anything in the 4s is easier to find.

I drill and tap for a small plug, to be installed right where the line-pressure adjuster is. That way I only take the pan off once, and can mess with the pressure all I want to. Make adjustments in small increments. No more than 1/2 turn initially, 'til you see how your tranny responds.