I have a LGB train that I setup for christmas and noticed that many of the LGB train cars I look at (mostly christmas cars on ebay) have 2 axles per car. All the cars in my set have 4 axles per car and it seems to me it would look odd to have some with 2 and some with 4 axles. Is there any significance to this difference and is is possible to convert a 2 axle car to 4 axles?