https://www.youtube.com/watch?v=fo3t_5-Hwo4 You might look what this guy did, I personally think and me being a modeler first and a train runner second that the drop bottom gondola is probably one of the hardest and most difficult cars to build. There are plans in HOn3 kits that you could enlarge and go from there, I personally have an HOn3 D&RGW layout and I have several Blackstone drop bottom gons on my layout and I didn't build any of them, Blackstone sells ready to run models. All being said, for the average guy I would purchase LGB 4076 Hopper cars, they open at the bottom in four places and would probably work better then these gons, you can find them on eBay at all different prices, I purchased mine for around $50 per car. I don't see any way to work with that car and get good results, maybe someone else has and can give you some good advice.
trainman