not a good way
because per item have a bonus amount limit
pc.hpp
#define MAX_PC_BONUS 10
if items effect item id to be dropped when killing a monster Treasure Chests race (RC2_TREASURE)
RC2_TREASURE,1324,1325,1326,1327,1328,1329,1330,1331,1332,1333,1334,1335,1336,1337,1338,1339,1340,1341,1342,1343,1344,1345,1346,1347,1348,1349,1350,1351,1352,1353,1354,1355,1356,1357,1358,1359,1360,1361,1362,1363,1938,1939,1940,1941,1942,1943,1944,1945,1946,2452,2453,2454,2455,2456,2457,2458,2459,2460,2461,2462
bonus2 bAddMonsterDropItem need write 60 times....