Ive been doing ebay since 1999 with over 5000 transactions and shipping my various bridge since 2007. I have found that I hate packaging, however it is by far the most important segment of the entire transaction no matter if it is a simple part or a large/fragile configuration. I normally package trains and train parts w bubble wrap covered by thick newspaper or equal. Then install into appropriate size box and fill any gaps w additional filler materials. I package my bridges in a very similar process. I frequently receive messages on how great the packaging was. Anyhow, my 3 cents worth.
jim r