Well...my HO layout is set at 42" to the railheads and if I had it to do over again, I'd make it 48". When the viewer has a "helicopter view" of a layout, it always tends to somewhat detract from any impression of realism. Such a height may not be suitable if the expectation is to share the layout with your children but it sure is a far better choice for an all adult audience.
CNJ999
CNJ999