Oh, yes - 66 (33+33) is only for modern russian cyrillic characters and as I can see on that Wikipedia page cyrillic family is HUGE
Probably there are some strong reasons to add a few additional characters to extend your cyrillic family to complete Ukranian (40 mln. native speakers) and Belarusian (10 mln. native speakers) alphabets:
0490 and 0491 - Ukranian and obsolete in Belarusian
0404 and 0454 - Ukranian
0406 and 0456 - Ukranian and Belarusian
0407 and 0457 - Ukranian
040E and 045E - Belarusian
And you may even support Serbian (11 mln. native speakers):
0402 and 0452
0409 and 0459
040A and 045A
040B and 045B
040F and 045F
Bulgarian alphabet can be covered by Russian characters only - visual difference is insignificant.
A few additional characters are needed to complete Macedonian and Abkhazian alphabets, but they are used not so widely as previous ones...
P.S. See
http://en.wikipedia.org/wiki/List_of_Cyrillic_letters