Hard pannier liner, spray on rubber
 

If your Alloy pannier liners wear out, try a spray on liner like used for truck beds.
tough stuff, thinner too. here is a link to a guy who did his whole bike,
http://www.finishlinewest.com/line-x_coatings.htm
I havent done this (pannier liiner) but I dont know why it wouldn't work, you will give up some cushioning for the gain in space.
Just a thought if anyone tries this post results please

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