Just do fresco. Closest thing you'll get to looking like flannel. The lightest or second lightest gray Minnis are perfect. Slightly varigated color and will wear reasonably cool. Be sure to specify unlined.
The Tenderloin has been a slum since Dashiell Hammett lived in there in the 1920s. The reason it 's still a slum is policy. The land is obviously mega-valuable. The libs who run the city think it would be a human tragedy to eliminate the last great urban slum in the middle of any otherwise functional American city. Junkies, hookers, thieves, etc. "deserve" a nice location. So the Tenderloin will never be allowed to improve.
I only got one suit from NSM. The pents fit really well. The jacket I think is tight and a little too racy. I don't like it as much as either Solito or Formosa.
However, I have gone back to them for odd trousers and would again, if I needed any.