I pulled out a few old HO freight cars and sat them on my layout, they were huge 
and looked like it could fill my basement quick. Then I was thinking I could get a Proto 2000 0-8-0, at least I wouldn't have to add ash pan detail. Looked at the HO model, no ash pan detail 
Yeah, HO does seem huge to me, too, after being in N scale for fifteen years. It's becoming less shocking as I become reintroduced to HO, but, despite building a number of HO layouts as a kid, I am surprised by how much my N scale experience affected my view of HO.
Coincidentally, my wife came in the layout room last night, and she commented on how enormous the HO trains seemed to her. It's important to note that the only exposure to model railroading that she has had is my N scale trains. When I tried to explain that the HO layout really doesn't take up that much more space than the old N scale layout, when you factor aisle space and the additions tacked onto the N scale layout, she didn't buy it.
DFF
