Let me know if you want rolls for the summoning(s). I doubt he needs to summon Force 6 spirits, so give me a ballpark of what is needed to achieve our goals and I can do the rolls, or we can just gloss over it and chalk it up to fluff since we seem to have the actual construction well in hand without them.
When we're ready to settle down, Ohanzee will summon a spirit to help keep watch. Either an air spirit for concealment, Man for illusions/invisibility, Water for detection, or Beast for a more proactive defense. Technically, Beast has the same chance of detecting as Water and would include that service as part of guarding, so it's kind of a two-fer. Likewise, Man has concealment, allowing a two-fer replacing Air, but phrasing a task to fit into Manipulation when really it would be concealment might be tricky (but would be required anyway if we wanted to use Man for his invisibility/illusions). I think we should rely on mundane camouflage and just stick with the Beast spirit on guard duty. Hiding under so much water (in the form of ice) should kill pretty much any astral or matrix attempts to locate us, so we're mostly concerned with physical security or dumb luck (which, considering Tecumseh's rolling history, is a distinct possibility).
At any rate, Ohanzee is fine with taking a watch and the photos.