i came accross a duplication glitch within this mod..using the crafting grid in the backpacks, you can place the items in the correct spots for the recipe, then close the backpack menu getting the ingredients back, and open the backpack back up and take the crafting item as well..im using zombie pigman bacpack..a suggestion would be make the crafting table storage too so it doesnt drop when u close it..

Done. Fixed for next release.

I also would like to confirm this issue.

Can also confirm this is an issue, but only when the backpack is being worn.

However, I can also give you the fix :
ContainerBackpack.java, onContainerClosed() needs to update the crafting grid by calling this.onCraftMatrixChanged(craftMatrix); - currently, this isn't being done, and the last crafting result persists between opening/closing (when being worn). Updating the craftMatrix after emptying it will result in expected functionality (crafting result is emptied when the backpack is closed).

I havent been able to replicate this. However, I placed don't checks to avoid that in case it tries to happen again.

So can I download a newer version, or is it being put together?

that wouldn't be a bad idea @xaleb. Sortof like the factorization portable crafting whatever-it's-called. You can fill up your entire inventory, but if you do, then you have to clear it if you want to craft on the go. I guess it could be the same with backpacks. You can fill up the entire thing, but if you do, then you can't craft in it. Also, it would be very convenient, just like the tinker's construct crafting station. If you are missing something, you can leave the crafting station, get what you need, and when you go back to the crafting station, everything is still there! It could be the same with the backpack crafting grid.

using a pack that includes AventureBackpack2 (Beta-0.8 if you believe the release notes) In the simplify: taste of vanilla (technic pack) RC1.5 I was able to recreate this dupe using several different backpacks in multiplayer.

mac os-x, I'll try it on a windows minecraft client next I remember.
1.7.10 btw.