Great layout. I’m building a new basement,er house and will be modeling in HO the Clinchfield from Kingsport to points north.Sometimes , however, I’m tempted to switch to O guage because of the added realislm due to its size. Curves are a concern as they take up so much room. What do you feel is an acceptable minimum radius for O guage utilizing mid 60’s era equipment(85 ft cars etc.)?