Myself and others have found that if you are wanting to replicate a wooden bodied wagon or a wooden underframe then the best way to go about it is through the use of plastic, resin, wood or whitemetal. This is because if you are using sheet metal or metal sections, it just simply would not be able to accurately represent what you want it to look like. And whilst it would be ok for steel underframes or metal bodies stock, it just won't capture the chunkiness quite as good. However despite me saying this, it is not impossible and some manufactures do indeed do this and the results can be quite good, examples can be found in the bill Bedford range and also D&S models.