Codex: Astra Copywritum, Page 118 wrote:This model may take either two sponsons, or four sponsons; each sponson is equipped with a lascannon and either a twin heavy bolter or twin heavy flamer.
To me this reads that each sponson can independently be given a twin heavy bolter or twin heavy flamer, the pairs of sponsons do not need to match. If they had to match it would say "each pair of sponsons" or something to that effect.
I checked the
FAQ and there was no mention of this. Am I missing something or is the assumption they need to match simply edition lag?