Primate lodge tree house now has mosquito nets and you can request chairs, drinks etc to be brought. Not for the fainthearted as it is a long way from the lodge but what a dawn chorus !!!!
I was charged 40,000 US as a single occupancy which was very reasonable
I too spent 4 hours chimp treking but found no chimps on the ground-only in the trees and hard to see. Fantastic walk though and Silva is a most knowlegdable guide. For guaranteed viewings try your local Zoo