Play normally.
Only pick up 35-slot backpacks.
When you find a new backpack, place your current backpack inside the empty backpack on the ground, then place that new backpack on your back. This will essentially add 10 inventory slots to the total amount of gear you can find.
Do this with about a dozen backpacks stacked inside each other.
Now join a new server..
Expect that new server to crash within a couple minutes. None of your gear will be accessible, useful, moveable.. so it's pointless to play like this for any reason other than to crash servers.