On this image I used the TC20EII and the TC14EII stacked,
then connected to the 300mm F2.8 AF-S lens.
To stack Nikon converters I cut the small tab off the 1.4,
which is a block to keep us from mounting our converters
on non AF-S lenses. After removing that metal tab, I can
place the unaltered 2X on the altered 1.4, making a total
of 2.4X. The 300mm becomes roughly a 840mm f6.3

The Nikon D2X seems to focus this combo very well.
Also, my 500mm F4 AF-I locks on focus using this stack,
however my 400 F2.8 AF-S refuses to focus,
it hunts for focus and will not lock on. Some suggest
the altered converters will work on non AF-S lenses,
but none of mine will. Also, the altered 1.4 will not work
on the new TC17EII converter. Don't try it! The rear element of
the 17 will be damages as it protrudes out and will suffer damage.