Instructions:
Download the zip, and extract it. Go in it, and copy the folder there (it weirdly put it in another folder, sorry, don't know why), into the XMLMods folder in your AI War 2 directory.
Once it's in there, go to PlayerData, in the same directory, and open XMLLoadingOrder.
Under _Vanilla, put "PuffinBuildForceField" (remove the quotes).
Should now be able to construct them from any command station.
Should note that you'd want to take these out once the new update hits, as this'd override that. Just remove the line from XMLLoadingOrder, and the folder from XMLMods.
(For devs: The problem was merely they weren't set to be in the Defenses build menu).
