I have not done that, however, you can always rename the file after it has been saved
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Save( "$temp\Big Class.jmp" );
rc1 = Rename File( "$TEMP/Big Class.jmp", "namewithoutanextension" );
show(files in directory("$TEMP"));
Close( dt, "NoSave" );
Jim