Found the perfect addon to my 26L GR1. An addl. 4 liters I use for doggo stuff and that doesn't make it look like a Tetris-bag. (Tasmanian Tiger Tac Pouch 10) :
Tasmanian Tiger Tac Pouch 4, Tactical MOLLE System Loops with YKK Zippers, Coyote - Walmart.com