Arranging my small, rectangular science classroom?

I teach 8th grade science in a long, very skinny, rectangular shaped classroom. My smart board is on the front short wall of the rectangle and cannot be moved. Since it's science, and I value group work extensively, the tables (which seat two students) are arranged in pods so there are 4 kids at a pod. My problem is that the kids in the back three tables seem SO far away from me and I feel like I lose them every time I am at the front of the room doing stuff on the smart board. I welcome any suggestions you all might have for arrangements of tables or even for ways to better engage and monitor the students in the back. Also, I change seats about every 6 weeks, so the kids in the back do come to the front and vice versa.

Here is a sample floorplan of my current room. Where it says "teacher desk" is my smartboard/podium area: http://i.imgur.com/xRj3vlm.png

Thanks!