The app will let you add the Wifi point but it's not recommended. The reason using more than 5 is not recommended is because Nest Wifi uses a "fewest hops" approach to getting traffic to its destination, so if one of your routers can get even a weak connection to your primary router, it will use that instead of going through another intermediate router. If you think you're going to need that many, a wired connection to each of your routers would be significantly more reliable (typically known as wired backhaul). If that's not possible, it's essentially a must to have your router centrally placed. Typically, it just won't be enough if the most distant routers are far away and if you really need that many routers, only wiring them is going to make the performance in that kind of setup satisfactory. That said, Wifi signal and coverage depends on so many different factors, so it's not an exact science, and you may be fortunate enough to not notice any issues for how many devices you have and the speed you're looking for. To that end, I'd recommend keeping the receipt if you go ahead so you can return it if needed.
