I would translate the config from 6 to 8 without the migration tool. Once that's done, and if the environment can run on one controller for a test, I would convert one of the controllers to AOSv8, and test the environment. Move some of the APs that have the PSK clients on them to the upgraded controller and test.
Take a backup of the controller to fail back quicker if needed.
Have you migrated licenses to the vMMs yet?
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Dustin Burns
Senior Mobility and Access Engineer @WEI
ACCX 1271| ACMX 509| ACSP | ACDA | MVP Guru 2021
If my post was useful accept solution and/or give kudos
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