Hi Spiros, when you say the pyramid encodes the number 5, do you refer to the number of secret chambers in the sanctuary of Thoth that Khufu wanted to incorporate in his pyramid according to the legend of the papyrus Westcar?
The secret number isn't revealed in this story but it is tempting to assume it is five since one of the titles of the architect of the GP, Hemiunu, is "greatest of the five of the house of Thoth" (this title is not exclusive to Hemiunu, but occurs IIRC not that frequently either).
When you start looking for certain numbers in a big structure like the GP you will undoubtly find them (and some if not all due to pure coincidence).
IMHO, the two examples you give are rather bad ones, no offence, since queen's pyramid G I-c wasn't originally planned and I doubt the gematria value of the Greek word for five has anything to do with te GP. But if you look long enough you can find quite some examples; I did the test and came up with the following: 5 relieving chambers above the King's chamber / the walls of the kings chamber consist of 5 courses of stone / the niche in de Queen's chamber represents a 5 stepped pyramid / there are 5 shafts that point to the heavens (at least according to some theories); 2 in the KC, 2 in the QC, the last one de descending passage itself / there are 5 boat pits belonging to Khufu.

I'm afraid the "5th chamber" will turn out to be a space used during the construction of the pyramid or a relieving chamber with nothing in it save perhaps some builders grafitti.
I hope however it will turn out to be Khufu's actual burial or even a "secret chamber of Thoth" because that would be so much cooler ;-)