I didn't change very much to modify this from the HO orginal. I skipped the turnbuckles and simplified the brick trim, made the hatch on top closed instead of open, used waxed thread instead of chain, and that's about it.
It was actually a little easier than I thought it would be. I used a painted toothpick with a blob of Sculpey as the spire on top. Another toothpick worked very nicely to keep each of the support pieces under the tank properly spaced. About the trickiest part was the bands around the tank.
Blurry shot, but it's just for size reference. I'll try to take some better shots this weekend.