[pdftex] pdftex not finding glyphs?

[Geoffrey Alan Washburn]

	I've been working on preparing the necessary configuration so that I 
can make use of some specific glyphs in the DejaVu Sans and DejaVu Sans 
Mono fonts.  However, I'm encountering a strange problem.
In my custom encoding file:

...
% 0xC0
   /.c0x2293 /.c0x2294 /zero /zero
...

I'm using .c0x???? because that is what ttf2tfm seems to use, though I 
have also tried uni???? with ttf2afm => afm2tfm.  When ttf2tfm is 
generating the metrics, it complains about a few characters being 
missing, but doesn't report any errors about these two particular 
glyphs.  However, when I go to build my document I'm told

...
Warning: pdflatex (file fonts/DejaVuSans.ttf): glyph `.c0x2293' not found

Warning: pdflatex (file fonts/DejaVuSans.ttf): glyph `.c0x2294' not found
...

Alternately if I use ttf2afm => afm2tfm path I get a different error:

...
Missing character: There is no <C0> in font IFMLDejaVuSans!
Missing character: There is no <C1> in font IFMLDejaVuSans!
...

I verified with FontForge that DejaVuSans.ttf does actually contain 
these two glyphs at the usual Unicode locations.

Does anyone have any idea where things may be going wrong?  It isn't 
clear whether the problem is in the font itself somehow, the methods by 
which I generate the font metrics, or pdftex itself.