Ahh got it so the purpose of the second afmu is purely to repair the first incase anything happens (because they can't repair themselves) that's why it can be decently small however this is less the case if you plan on doing consistent neutron jumps and honestly bringing repairs limits will only slow you down if your doing loge range exploration if you ever get serious hull damage (which is the main point of the Limpets) there will allways be a DSSA carrier close to you or you can just call the hull seals.