With such a long wheelbase (distance between wheels), it will be pretty hard to turn, especially with those Hi-Grip wheels from FIRST. Old kit of parts wheels weren't as grippy, although the ones you're using won't be very maneuverable in your setup.

If you can, try making it a 6 wheel drive with the center wheel on each side lowered a bit. This effectively creates two smaller wheelbases your robot can rock back and forth on as well as giving the more stability of a long robot drive. It's one of the most popular drives in all of FIRST, and is by far one of the most successful ones. For more information on how to make one, visit 1114's Drivetrain page and read up as much as you can. Don't read too much, though. You still have a robot to finish!

Good luck these next few days, and I hope you have a great season!