I've been using a rack on my Marinoni for all my brevets for 5 years now.
I'm also a Carradice user.
My Carradice bag rests on my rack!
However, for shorter rides, I just strap a small bag with a few tools in it onto the rack and go. Works great!
Edit: I added a photo of my Carradice + rack option below. Going with one does not mean you can't use the other. Both together work very well. That photo was taken at the beginning of a 200K brevet last year. This year, I didn't use my Carradice for anything under 400K brevet, instead I used much smaller trunk bags. But that's the beautiful thing about a rack ... you can carry practically nothing at all for relatively short rides ... or go with a larger bag like a Carradice for longer rides.
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