Having looked at the use of the Private Use Area in Garava and in Code2000 and having looked at the Private Use Area mappings mentioned by Bhikkhu Pesala in the Problems Mapping thread, I have come to the conclusion that a good choice for the value of X would be F.
Thus the mappings would be as follows.
U+EF0. A
U+EF1. a
U+EF2. E
U+EF3. e
U+EF4. I
U+EF5. i
U+EF6. M
U+EF7. m
U+EF8. N
U+EF9. n
U+EFA. O
U+EFB. o
U+EFC. U
U+EFD. u
U+EFE. Y
U+EFF. y
…0 grave
…1 acute
…2 circumflex
…3 tilde
…4 macron
…5 diaeresis
…6 hook
…7 ring
…8 caron
…9 vertical line
I would map the special small N to U+EF8F.
For example, in the above, e acute would be U+EF31, but I would not use that as e acute has the regular Unicode assignment of U+00E9 so I would use U+00E9 for e acute.
For example, in the above, m vertical line would be U+EF79.
Of the 161 characters, some are in regular Unicode and some are not.
I know that m macron is not in regular Unicode and, as m is both a character of a width greater than most characters and is a lowercase character, perhaps m macron might be a good example because it is likely to be more difficult than most of the other characters to implement.
Also, please note that to implement the accented characters using i, a dotless i character will be needed. Garava already has a dotless i character so that is not a problem, yet I mention that in case you also try to implement using other fonts.
I suppose that those of the 161 characters which are not in regular Unicode could be added one by one manually into the Private Use Area, but I suspect that a transform script could be written which could then be used to add the required glyphs to any font: there would still need to be some manual adjustment of the positions of the accents, but most of the work would have been done by the Glyph Transformer.
William Overington
19 November 2007