[Banned]

It's not as simple as 'fortress galaxies work' or 'don't work'. We had one fortress galaxy fail spectacularly (11.6, the shitty quitgal). And while 3 of our heavy gals are top10, we also have 3 gals with >8 members outside the top10. It's no guarantee.

I'd say that there are very definite advantages that have a good synergy effect with other Ascendancy policies. Whether these advantages play out the same way in an alliance with appointed DCs and idiot members who don't build solid fleets isn't really for me to say.

One of the advantages for us is that way more members ground attack fleets to defend when a fortress gal has heavy incoming. Our 3 biggest gals swapped defense like this quite a lot. I think the primary advantage is aligned interest. If you have a fencegal, what is in your interest may not be in the interest of your alliance. With a fortress gal it's pretty simple. What is in your alliance's interest is in your galaxy's interest.

Edit: Oh yeah, and outside of wars the political protection offered by being in a fortress galaxy is great. Everyone knows that galraiding 2.10/6.1/7.8 is tantamount to planet targeting Ascendancy, so can't really do it without risking fallout. This protects our non-Ascendancy galmates (yes, we have some!) allowing them to grow larger fleets which they in turn use more aggressively ingal when they see how much ingal backing they get (at least it tends to get like this in the fortress galaxies I've been in, I doubt it's always like this).