Remove it as much as you can, redistribute it if you can't, and add it only if you have no other choice

I felt compelled at the spur of the moment to throw down the best lesson I learned during my time playing SImpleplanes that people who are new to this game (as well as engineering-centric games as a whole) might not understand the importance of. Less weight generally translates to less energy payout required to get you moving, which translates to less fuel required to keep you going, which translates to longer ranges and higher performance. If you're on career mode, less weight also means lower launch costs across the board, resulting in a lot of cumulative savings over time.

I had been ruminating on the usage of dead weight in crafts. I remembered that the only time I've ever had to actually use dead weight for a practical purpose was on a ballast to stabilize a boat in Stormworks, but eventually I ended up rebuilding that boat from the ground up to redistribute it's inherent center of mass to underneath the waterline, and I gave it a small weight connected to a rotator that used the value of the ship's roll as an input to spin the rotator, which acted as a rudimentary gyroscopic stabilizer. While the system used up some electricity, it ended up being a far lighter alternative to a static ballast, which would have resulted in less speed and higher fuel consumption. So the point I'm trying to make is that even if you think adding weight is your only option, it realistically, probably isn't.