I have to admit, I did it today.
I added the malt pipe, bottom screens then the grain. I added the top fine screen & then the phone rang. Spoke briefly to the missus who was at work & put on the cross bar at the top, done it up tight & hit go. Just as the malt pipe was overflowing, I noticed that I forgot the top stainless solid screen, ****! I hit abort & due to me seeing it so quickly, I had no issues with grain in the wort. It's easy to do & I guarantee I won't do it again. Ended up being a great brewday, just a simple Cream Ale. 50lt into the fermenter @1.051. Much better than my predicted 75% so I'll make a couple of changes next time.