...
> 1) How can I get the COPY command in the 2nd to the last line
> to APPEND the
> contents of SMAF25 to STRSCOMB, without overwriting it?

No, not even via a file equation specifying ;acc=append.
COPY will want to purge the TO= file if it already exists.

> Should I consider using the FCOPY command instead as in the old UDC?

Yes, or you can use CAT.HPBIN.SYS which is the POSIX shell's cat
command.  You may have more questions if you decide to use cat.

> 2) I'm not sure if the REC= parameters in my file equations
> are absolutely necessary. On the other hand, will it hurt to leave
> them in?

Assuming the program, RTSMAF.PRNSCH.QSSPROD, does not reference these
file equations you probably should delete them.  Their existence could
cause confusion for someone (else) maintaining these UDCs.

regards,
Jeff Vance, CSY