Hi Hans,
Its been suggested (I don't remember who by) that Khufu's sarcophagus chamber was partitioned into two separate compartments that represented the Duat and Akhet from which he emerged into the sky. The partition either took the form of a free standing light wooden structure or a wooden framework with a covering of linen cloth. There is no direct evidence for this however.
Khufu's sarcophagus chamber is 20 x 10 cubits, and an Early dynastic royal tomb about 2.4 km SSE from Khufu's pyramid had a similar size of stone built burial chamber approx. 20.6 x 10.7 cubits, and it did have a wooden inner chamber built inside.
The Grand Gallery may have had a separate wooden ceiling - Lepre suggested cedar panels inlaid with gold, set into 180 mm high and 25mm deep grooves that run the whole length of the gallery. (Lepre 1990: 82-3)
CT