My editor only supports 4 digits due to the size of the idfile member in the item_struct. As you're probably aware the top of the Item_Struct is ..
char name[35];
char lore[60];
char idfile[6];
sint16 flag;
.. and the item graphic is stored as a non-terminated string inside idfile. As all of the items start with "IT" I could only have 4 digits without corrupting 'flag'.
This puzzled me greatly as I've been finding unique items well into 5 digits when I ignored the badness I was doing by writing over 'flag' with random numbers. I never worked out what was really going on, so I left it at 4 digits
You'll have a hard time changing that behaviour in my editor I'd have thought Baron, unless you made 'flag' an 8 bit number and made idfile[7]. But that's bound to screw up a load of items :(
K.