Our hi-rail layout was 6x10. You can see pics of it in my link below. We dismantled it in 2006.
The big thing is to not be in a hurry and don't cut corners to save time. I regretted not elevating the right-of-way by a few inches. I didn't want to take the time to do it and, unfortunately, the layout always felt "flat" to me. I also skimped on the brand of switches used and thus, operations always suffered as a result. My wiring practices got more sloppy as I progressed as well.
Had I not made those errors, we may have never dismantled it.
