I show below a photo of the Athearn bonnet, with platform removed, followed by a photo of the same car with a replacement scale-size bonnet, which is Precision Scale’s part #31005. The difference is pretty evident. (Note also in these two photos that Athearn has used the riveted-tank bottom sheet--all those rivets should be removed for an insulated and jacketed car.) As a basis for comparison, I also show a prototype photo of a car of this size (around 11,000 gallons—an AC&F photo courtesy of Ed Kaminski), and a photo of an unmodified Athearn “chemical” tank body.
Whether or not the car you are modeling has a platform around the bonnet or merely a walkway (like the prototype car shown), the bonnet size needs to be corrected for these cars to look “right.” And this is an easy fix. I will post later on my completed model, and on the problems of correcting the Athearn dome platform if your prototype needs one.
One last comment: isn’t this just a poor version of the recent Atlas HO scale LPG cars? Well, kind of, but not exactly. The Atlas car is about the same gallonage but is a somewhat shorter and fatter tank, and has an AC&F underframe, while the Athearn car has a General American underframe. To me, they are different cars and for variety, I want both models in my population of tank cars.