I'm planning my V5R4 conversion to 7.1 The 6.1 Memo to users has the

Device files may experience performance problems.
Application programs that use printer, display, and communications device file (*FILE) objects might run slower after upgrading a system to the IBM i 6.1 release. Enhancements were made in 6.1 to further protect system data at the beginning of the *FILE objects from accidental or intentional tampering. Device files created on 6.1 will not experience a performance degradation. Existing device file objects will be automatically converted the first time the file objects are restored from a save file or save media and will not experience a performance degradation after the files are converted.

IBM Support line seems to have no idea what the extent of this problem is, how to detect what files (DSPF PRTF CMNF) will cause this, nor do they have a reasonable solution other than to restore the device files.

I have no desire to restore thousands of device files to many different libraries after doing a weekend-long upgrade process. Nor do I relish waiting around to see if anyone squawks about the bad performance of the "new, improved" upgrade -- not a stellar way to convince users that IBM i is the way to go.

Has anyone seen this behavior after an upgrade from V5R4 to either V6R1 or 7.1?
Were you able to fix it somehow?