MultiInv can't record special data like below picture.

http://i.imgur.com/fqHOKQ3.png

http://i.imgur.com/fUpVg1W.png

like -200 Attack Damage.

When MultiInv load this item to inventory.

The special data will disapear.

This is my player.dat you can look NBT node of this item.

http://www.mediafire.com/?dhevn6i2wmgiuvk

I'll take a look at it and see if there is an API for it in bukkit. If not I'll be waiting on that.

But some other plugin use custom NBTTag for saving extra information in items. example:MobCatcher.

I think record NBTTag is the best solution.

It is simple to record NBTTag. Just serialize the root of item's NBTTag.

No more than 10 line code.

Serialize all of inventory Sample Code:
https://github.com/yukinoraru/ToggleInventory/blob/master/src/main/java/com/github/yukinoraru/ToggleInventory/ItemSerialization.java

Some other reference data.

http://imgur.com/a/Mh3fa

I hope MultiInv can support ALL ITEMS include custom items which using NBTTag.

Like this plugin http://dev.bukkit.org/bukkit-plugins/toggleinventory/