My recipe using the same 383gr of shot and TPS wad did not call for a card or anything under the wad. I found I had a powder migration issue with Cheddite hulls. The TPS wad is concave under by design, and gas seal doesn't make good contact with the hull wall in the shell. I've heard of two methods to help with the seal. One I've tried.
I've taken a piece of tyvek ( usps mailer ) cut it and then started the wad into the hull. Just enough to crease the tyvek. Remove it, and trim so that I have maybe an 1/8" cup. I use this under the wad. It conforms to the concave of the bottom of the wad when you apply your wad pressure, and seals the powder so migration isn't an issue.
Question might be pressure variations using an over shot card, or spacer. Just thinking out loud.
Second method I heard about is using a steel ball to make the gas seal on the bottom of the wad a little more pronounced. This would keep it so it matches my recipe exactly, no tyvek.