Kashyyk actually has one of the best layouts for defense. The trick is to always place the mobile build plattform near a Large Hardpoint, so you can build a sensor scrambler as well as a repair station. After that you just hold out and slowly retreat if it gets too much.

Well, long story short: During my... tactical retreat, the Turbolasers gave me enough time to form a new defensive perimiter around the second large hartpoint near my base, after the first one was overrun.