for the X3, we could try to use the larger parachutes which provide more drag and are less likely to snap off, which could be an issue in the thicker atmosphere.
KSS Station: 8x18x11 I built this before I saw this challenge but nonetheless I submitted it. I used parts from Nova Punch (rocket) and the BACE mod and Probodobodyne Mod (station). It handled like a brick in orbit. (rcs ran out)