What i am suggesting is to increase the stack size of Fuel and Concrete to 200 (currently at 100).
In my opinion it would make a lot of sense for Fuel since Biofuel already stacks to 200 items so i have no idea why it's not the same for Fuel. This would help exploration a lot as having to take 4/5 stacks of Fuel for a long exploration sessions realy reduces the amount of free inventory slots to pick random stuff up.
For Concrete, it's really annoying to have to refill your inventory constantly in order to build a large flat area which is necessary to place a lot of machines. Having the stack size increased to 200 has no negative aspect and would divide by 2 the number of round trip to your concrete farm that you have to do. Furthemore it would also help exploration as you always have some concrete in your inventory while exploring in order to build bridges or climb up cliffs, having them in larger stacks would free even more inventory slots !
tl;dr make Fuel and Concrete stack size to 200 to free up more inventory space while exploring and building large plateforms !