Inconsistent shifting: any ideas?

So it isnt the shift point that changes, just the shift quality. I dont believe that this is related to governor weights or kickdown linkage.

I would suspect that it could be related to fluid temp. Did it shift best early in the day when the fluid was cooler? Do you have a good cooler installed?

Do you have a deep pan? If so is the filter extension installed?

Type F fluid causes firmer shifts if you wanted to try changing it.