[JackR]

It’s been a saga, but I (the OP) am happy to report that PSA decided to process my crossover request at my minimum requested grade.

Whether they reconsidered their initial decision to “remove the minimum grade option from the submission process,” I don’t know. Their web page and application form still appear to allow it, but an FAQ apparently said the policy had been temporarily suspended.

In looking back on this episode, I have to agree with the comment by Rick Clemens: “I sill prefer to buy PSA cards but hate submitting them. It’s awful.”