CPYF FROMKEY/TOKEY using packed key field

Monday moanin' moment...

Keep getting CPF2951 (TOKEY comparisons not correct for from-file) when
trying to use:
CPYF ... FROMKEY(1 (X'61200000000F')) TOKEY(1 (X'61299999999F'))
or
CPYF ... FROMKEY(*BLDKEY (61200000000)) TOKEY(*BLDKEY (61299999999))

The key in the file is one field, an 11-digit packed (6 byte) field.

To test that it was copying the correct fields, I also tried:
CPYF ... INCREL((*IF CSC# *GE 61200000000) (*AND CSC# *LE 61299999999))
... and got the same result of data without the CPF2951.

FWIW, the FROMFILE is a logical file and the TOFILE is, as required by CPYF,
a physical file.

Anybody know how to use FROMKEY/TOKEY on a packed key field and avoid
CPF2951?

Anybody know from experience whether the CPYF process is "smart enough" to
see that INCREL is specifying the first *N key field(s) and, effectively,
read by key to limit the records it reads to copy? (As opposed to reading
every record in the file, and selecting only the INCREL hits?)

TIA, Dan