My word, Valencia handles most oddly with one Ortlieb back roller full of all my work stuff, with a couple of boxes of porridge wedged in on top, and the other pannier full of 3kg flour, 2kg sugar, 2kg of marg/butter, couple of litres of OJ, 1kg of chocolate, couple of kg of dried fruit and some other bits and bobs. With lots of eggs precariously balanced on top. I suspect that my rack isn't technically meant to carry that much weight....
I can do baking now!