The big problem that I have encountered is availability of cars in CB&Q lettering and mineral red paint. Checking the Walters website today, nothing listed or in stock for the Proto2000 (now called WalthersProto), Stewart or Accurail hopper cars in my desired paint scheme. Same results for the Accurail website and the Bowser website. I could not find a website for Stewart. So, some good suggestions (I hadn't thought about Bowser, for example) but no manufacturer seems to have any currently available. Accurail does have C&S 55T 2 bay hoppers in stock, but for me that is only "close but no cigar". Perhaps some of you can tell us of current sources for these cars, other than the websites that I mentioned that proved fruitless.
And yes, I have thought about adding some more gondolas for this service. Still would like more hoppers, though. Maybe train shows (and eBay) are the only current source for such hopper models.
Scott Myers