I did not discover just sharing the info. Thanks & +rep apricated

NOTE: - works better the more full the server is (the laggier the server the more chance of success)
- modded servers can be less full (depending on how many mods there are)
- there cant be a queue or else it wont work

Dupe #1 (Requires Speed hack):
have what you want in your inv (backpacks are better as you only want to try to dupe a max of 2 items)
logout waiting the full timer (15-20 seconds)
now connected back to the server using the play last button
once you login get ready to drop the items you want to dupe
**this has to be done very quickly**
drop the items you want to dupe (max 2)
immediately use speedhack (it will disconnect you since the server disconnected you are able to reconnect before your character syncs
that you dropped items)

7 sec put cable back in
reconnect to the server AS FAST AS POSSIBLE (if you were fast enough boom items duped)

if you did not dupe try it with 1 item and be as fast as possible (speed is key)

Dupe #2 (No speed hack):
have what you want in your inv (backpacks are better as you only want to try to dupe a max of 2 items)
logout waiting the full timer (15-20 seconds)
now connected back to the server using the play last button
once you login get ready to drop the items you want to dupe
pull the lan cable, wait until the timer is at 6/7/8 sec, then put back in
as fast as possible reconnect