That looks like a great start! Its hard to model accurately without any real baseline for dimensional accuracy, but I think overall your proportions look pretty good. It's hard to tell for sure, but the only thing that I believe is throwing me off are the openings in the walls that obscure rider views left and right. They look a bit tall and elongated opposed to some images I saw online and thus make the overall form a tad stubby. Also, out of curiosity, what program are you using?
It's been a minute since I posted, and I haven't been in this particular thread for some, time so it is a funny coincidence that you are engaging in an RV model series. I too have a fascination with RVs and was also working on modeling some of my favorites out as well. I've started with JPRA (FL Version) and plan to 3D print it sometime in the future.
I was really inspired by the RV models that Universal Japan has at their guest services and I am hoping to emulate those. I'm thinking of possibly tackling the SCOOP, Kongfrontation Tram, or Jaws boat next. For JPRA I still need to model the uplift wheel assemblies but I am having trouble finding some clear images to reference. So I will probably go over to the park see if I can get some myself, just didn't have time this weekend. Anyway, sorry for the wall of text, here are some images of it below.
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