If there are no conflicting files in the exedir, extract GAME.CON, DEFS.CON, and USER.CON from DUKE3D.GRP to prevent conflicts in other GRPs and folders.
Prevent formation of a CON incompatibility (rename GAME.CON, DEFS.CON, and USER.CON to VACA*.CON) when constructing the VACA13.SSI-based GRP.