Finally getting back to (hopefully!) playing some, and my shiny new Pacto POD just arrived. Looks very nice, and I can't argue on the value for money front :)
page 37, 3.B FLEXIBLE MOUNTED IN SKIRMISH FORM
Point 6 says "they need to be 3-deep to shoot at full effect (2 for Magna").
Thanks for letting us know. I have updated the official errata.