Originally Posted by C W Burfle:
IMHO, tempered hardboard would be unsuitable because it has too much flex. Also, it would not hold screws well.
I would go with plywood.
What are you are building?
Do you plan to frame the underside of the layout?
Is weight a consideration (does it have to be portable)?
Typically solid top train layouts require framing.
*The dimensions of the layout will be 42inches by 42inches I would prefer it to be portable.