One thing that is not mentioned in this article as a pre-requisite but should always be checked prior to proceeding with a migration is the Mailbox Database quotas that are in place. Public Folder mailboxes adhere to any Mailbox Database quotas in place for the mailbox database they reside under. You want to ensure the public folder content being migrated to each public folder mailbox does not exceed your mailbox database quota limit or you will run into issues during the migration.
In the event the public folder data being migrated does exceed your mailbox database quote, like with standard mailboxes you can increase the quota to the public folder mailbox to overwrite the database defaults with the following command.
Set-Mailbox PublicFolderMailbox -PublicFolder -IssueWarningQuota 1000MB -ProhibitSendQuota 1100MB -ProhibitSendReceiveQuota 1200MB -UseDatabaseQuotaDefaults $False
Make sure you check this prior to migration.