Hey There, here goes my lil hint about dupe itens...
The way there they are duping is via sending packets without disconnecting and some ingame tricks with trade:
player1 = normal client
player2 = OOG walker
*Player1 ask player2 for trade
*Player2 press no to trade invitation.
*Player2 invite player1 now for trade
*Player1 accept the trade
*Player2 gives player1 the items who wants to dupe and press ok
*Player1 press cancel and the trade will cancel
*Player2 must leave the items who wants to dupe in wh
((now set on the autoaccepting trades to your OOG walker [player2])*
*Player1 ask player2 for trade , when the invitation window apears player2 logged out as soon as he accepting the trade (dont worry about it , the option autoaccepting trades from OOG walker will do it for you) , now login..items duped , u will se that player2 will have the item that he duped in his inventory and the another one in the wh.
Yeah, I know, i`ve found this on another forum, but I just wanted to share. Also i tried it on Radt(l2j-IL). I didnt tested it on l2off... Sorry T_T
Good luck and have a nice dumping.