Technical Hydramatic mod for hard shifts?

I was reading up and watching vids on this trans. Mine is a 54 mated to a 331 Cad motor.
at 1:05 in the video this builder makes mention of a modification to alleviate hard shifts. Tell me what you think. Is he wrong?

 

You can shim the pressure spring with a washer or two. Under the Big hex nut driver side just behind the bellhousing, 11 o'clock.

 

Are you referring to the pressure regulator?

 

I'd heard to use "spark plug washers" to shim the spring being talked about here. They apparently fit into the recesses of the "big nut" and are the same diameter as the spring. I am Butch/56sedandelivery.

 

Gotta love the banter between the mechanic and the lady shooting the video!! Yes, spark plug washers do the deed very well. That is what I used on my Hydro.