I have the same scope for directories, I need to have them defined at 0750, instead of 0700:
# ls -lha /var/lib/nginx/fastcgi
total 4.0K
drwxr-x---. 6 nginx root 120 Aug 10 14:09 .
drwxr-xr-x. 9 root root 4.0K Aug 5 20:38 ..
drwx------. 3 nginx nginx 60 Aug 10 14:09 1
drwx------. 3 nginx nginx 60 Aug 10 14:09 3
drwx------. 3 nginx nginx 60 Aug 10 14:09 4
drwx------. 2 nginx root 40 Aug 10 14:09 cache

IF this is not possible with an option, can you please let me know if it will suffice to modify the source code on ngx_file.c and adjust:
*access = 0600;
ngx_create_dir(file->name.data, 0700) -- multiple locations