I was playing around with the solver on this sheet to optimize a design. Optimizing for Colonists/BP/hr/L results in a ship with one cryo module, one engine, and one tiny fuel tank. Optimizing for (Colonists/BP/hr)*(Colonists/L) gets me a more reasonable design with 35 cryo modules, 2 advanced CHS, 23 engines, and one standard fuel tank.
Maybe I'm just too tired at this hour, but I really expected the former to be the right optimization target. As expected, both designs are worse in Colonists/BP/hr than a design optimized just for Colonists/BP/hr, and both are worse on Colonists/L than a design optimized for Colonists/L, but the first design is much worse. Can you think of a reason for this to be a better optimization target?
BTW, the solver in LibreOffice works once you set up the right constraints (setting a constraint so that every variable is >= 0, is an integer, and so that it doesn't put a million tiny fuel tanks, etc) but the UI is annoying. To solve again in a different column you have to edit all of the constraints individually so that they point to the correct cells. I also had to restrict it to solving with only one type of engine, as it could never find its way out of the trap of putting in multiple types (which makes the design invalid). How does Excel compare?