are you going to try to mash in a low volume? you need enough water for the mash and then end up at 9.5L after the boil. the minimum to circulate the mash depends on how much grain is in the tube, so let's say you need 16 liters of water to circulate? i'm not super confident on that number, just kind of thinking out loud. then don't sparge and collect 11 liters?, boil down to 9.5?,,, could work.... but i think you are limited by 1. minimum amount of water needed to circulate and 2. amount of grain you can cram in and still get good circulation. point 1 depends on point 2, and point 2 depends on the grain itself, the crush, and probably the mash chemistry.