TBH sc can be baited way to easy!!! If attacked from the west corner your HQ can be taken out before sc get deployed!!!
Now I will suggest and it's only my point of view what's worked for me,,, keep SC an Deka's next to HQ and make sure you have all 3 shields covering the SC!! Then place turrents around main focus i.e HQ SC Deka's and then use all other building as walls to protect main focus,,,, topped with walls!!!
You can check out my progression and stat's on 'Jayjack rebel base designs',,,, I also have a level 8 post here to!!!
Jedi-Master's defence strategists!!!