passing parms between Cobol/400 & ILE-RPG

This is primarily an RPG shop that has a lot of legacy Cobol from a
non-IBM system that the AS/400 replaced years ago.  I am a relative
Cobol newbie (haven't done any meaningful Cobol coding since college).

Got a Cobol program (non-ILE) passing parameters to an ILE-RPG program.
 I am told by other RPG programmers here that also do a little Cobol
that to pass parameters between Cobol and RPG, you have to define the
*Entry parameter in RPG as one long string and define subfields in a
data structure.  If you try to define multiple PARMs for the parameter
list in the RPG program, the call will bomb with MCH3601.

The definition and the code in Cobol:
  01  1300RG-PARMS.
      05  P1300-COMPANY-IN       PIC X(4).
      05  P1300-CLIENT-CODE-IN   PIC X(5).
      05  P1300-JOBNUM-IN        PIC X(11).
      05  P1300-MODE             PIC X(1).
      05  P1300-TE-FLAG          PIC X(1).
      05  P1300-RTN-CODE         PIC X(2).
      05  P1300-ERR-MSG          PIC X(80).
---
         CALL 'PD1300RG' USING 1300RG-PARMS.

I assume that the USING phrase allows multiple fields.  True or False?
I am going on the assumption that it does, but I don't know if there
are special rules in the case of a Cobol program calling an RPG
program.  The Cobol manual I have makes the assumption when describing
the USING phrase that a Cobol program is calling another Cobol program,
so I don't know if this implies potential problems or other rules when
Cobol calls RPG.

Are there any references to Cobol calling RPG that would answer this
question for me?

TIA, Dan

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com