Started a layout using a 30"x80" hollow-core door with associated benchwork, about three years ago. Never got to track laying stage. Now I wi***o go to 4x8. Is it practical to attach to 4x8 on top of the door, or, should I build new framework?
Use the door as an extension to the 4x8. For the 4x8, use a very thin sheet of plywood with 2" or 4" thick of extruded foam glued on top. Attach legs (fold up variety is fine) to the plywood. The purpose is of the plywood is to spread the concentrated loads, not strength.