I don't run any spacer at all. I figured that I had enough Plenum volume!
Maybe I'll try running a couple 1/2" thick 4 hole ones under each carb.
Directly under the carb is just a big valley. I was thinking of making some sort of spacer shaped like a dome to help suspension or puddling. I can also reduce the plenum volume in numerous ways between the two carbs area.
