I used the same Atlas 20' containers but instead of over plating with styrene I sanded the sides and to flat. The undercarriage you built is almost identical to what I did, but I did simplyfy the towbar. I used Atlas 68' flatcars instead of 85' cars due to clearance issued in my railroad. The overall effect is quite good. I have built 6 wagons and decaled a panel an bought from Diecast Direct. Here are some pictues of my efforts to far.
Rolland