I’ve got the Mk2 QR Sport; interesting to see that it’s been discontinued. I confess that I’d probably have gone with a Mk1, but that wasn’t available when I purchased mine, only the non-QR version. There's quite a lot of "scaffolding" on the Mk2 - but I only use the stay on the non-brake side, eschewing the stay on the other side. It's still slightly lighter than a full rack.
And I find the QR *very* convenient. I have however lost TWO of the little QR release levers, which as the bolts are spring-loaded often means the bolt being ejected somewhere in my messy garage (I’ve not lost a bolt out on the road yet, but I have found myself riding with just one bolt engaged from time to time, and haven’t lost the bag).