Take a look at the Ibera RA5 rack ( and RakPak bags )
(Link Removed - No Longer Exists)
It is rated for 55 lbs vs the City Kit rack's 22 lbs ..
It will require bending of its front support rods and making a tapped aluminum block insert
to replace part of the stock ABS plastic one, but worth the effort : it is Strong !
And, Ibera makes several snapon-off bags of very high quality.
Alex