if the clutch pack is not below the minium stack height, then I would inspect all the plates. If the steel plates are not overheated and warped, then I have had very good success with the following:
1. round up a piece of plate glass, 12x12 inch or slightly bigger, tempered would be best.
2. spray contact cement
3. full sheet of 400 wet dry sand paper.
glue the paper to the glass
lightly sand the friction surfaces of steel plates while flushing the paper with fluid of choice (I use this setup in the solvent tank). Sand each side of the plates until there are no shiny spots. Now do the same to the friction plates (LIGHTLY!) to remove most of the burnished effect on the surface of the friction plates.
Flush well with solvent, blow clean/dry, cover all plates with oil and reassemble clutch.
will be butter smooth