If you don't want to count/estimate how many shields you'll have once out of despotism, I'd suggest counting how many tiles your capital can work and making sure you have 12 tiles with at least one shield of productivity possible. Of course, one can probably win a 20k game with a city with only 15 shields, although in Conquests that would seem a rather slow game. I'd suggest looking at how many shields you'll have once out of Despotism and aiming for at least 24 if not 25 shields in your 20k city. 27 shields will get your city to 40 shields in a non-despotic golden age. So, if you don't mind throwing more starts away, you might want to try for 27 shields since 40 spt is a good ratio. Looking for a start with anything more, in my opinion, might lead to rejecting other games which had more SGL potential or had something else nice going on, like easy access to ivory. Looking over one of my games which I haven't matched, I noticed I had 26 shields pre-Engineering and I didn't research Engineering until after I went to Free Artistry. So, I'd say 25 shields once out of Despotism.