Great map. I played against two AI on Hardest and, having struck out towards the centre to claim the higher-production planets towards the centre, failed to protect my back properly... so I ended up sandwiched between the two of them, completely surrounded and fighting battles on all sides! Oops!
I managed to gradually move my territory over to one side and let the AIs battle it out over my abandoned planets, resulting in my eventual victory. It was the most fun I've had playing the game for ages. Cheers.