I don't live in a high bike theft area. My seatpost has a bolt, not a QR. I U lock the frame and rear wheel to the rack, and then use a separate cable lock for the front wheel/frame to rack (2 kinds of tools required to cut it). My experience with QR seatposts is that they don't stay put.

I usually cover the saddle (when I rode a brooks) to protect it from moisture, and otherwise don't worry about it. I would NOT want to deal with getting a Brooks re-positioned on the seatpost, or the seatpost in the stem after every 1/2 trip.

PS - under search on the top of the forum, you can go to "advanced search" and search for keywords by thread or post. I don't specifically recall a discussion of this, though.