Paul-- The slipsheets are usually pretty beat up. Also, they're a LOT less rigid than luan. They're like a thick cardboard. I was experimenting with making a curved piece of base moulding. I laminated together about 8 pieces of this slipsheet material with regular yellow wood glue. I ended up...
"Compressed fiberboard" also includes what is more commonly called "hardboard" (in addition to MDF, as Paul mentioned). Hardboard is the stuff that pegboard is made from. Clear (non-perforated) hardboard is available at any building supply superstore. Sonotubes are spirally wound, laminated...