Don't get frustrated, you didn't explain yourself very well.
It wasn't until I took a look again at the code Techne generates that I realized I could just instantiate a new ModelRenderer class and .addBox a cube representing my tank of the appropriate dimensions at runtime and go from there.
Don't get me wrong, I am thankful for your help (and it did help give me the right idea). Frankly, I feel stupid for not realizing this earlier, but oh well