ftb 1.1.2 Canvas Bag Clone "cheat". Need help

Hi there,
we run a FTB Ultimate 1.1.2 Server. One of our player came across this video

wich explains how to use the Canvas Bag to duplicate items. We tested it and it works, unfortunately.
We really would like to get rid of this Bag. We choose the extra hard version with greg tech for a reason.
Out last server was a tekkit world with full EE included wich turned the server more or less into a creative mode.
Killing all the fun in the end.
So how can we get rid of this bag ? preferebly overwriting it with some other block so noone can secretly hide
one.