I use the digest on several lists successfully.  This is what I use:
 
*  DIGEST= yes,same,daily,14:00,size(2500)
 
This example is from WOODWORK@IPFWVM if you want to review the entire
header.
 
Larry Rondot
Rondot@IPFWVM      - or -      [log in to unmask]
 
BTW: I don't claim to have the last word on LISTSERV - Check out the
list archives for LSTSRV-L@UGA with LDBASE for complete details on
the syntax rules.