Attached a piece of corrugated plastic material I got at Home Depot to the first two ceiling joists so we could lean against them and not break the bamboo. Used the same screws and finish washers as with the bamboo.
It comes in 3x5ft sheets and is very lightweight and inexpensive. If the bamboo ceiling does not work out over time I plan on using this material for the whole ceiling. I think it's used for making stick-in-the-ground signs...