The run time also depends on where you feed the power. If you use the external power adapter port, you'll get less time than if you are using the modified sled/door connection. I never did that (too pussy to deface my deck) but those who did reported huge improvement in run time for the same set of cells.
Also, when you feed through the sled bay, the battery monitor appears and works as it should.
JFYI, I think that the sled option is only recommended for D-Cell packs, not SLAs.