Thet are Tamiya plastic tracks. Metal ones would work too. They are quite close the the upper hull. I did have to cut part of the lower hull ( you can't see it unless you are looking from underneath. All in all it worked out better than I thought. I picked up an old HL panther and I am going to do what you did and cut out the suspension arms and fit them in. I also thought about picking up those suspension rails you see on older Tiger 1s to support the suspension. I thnk that would also work.