>> the charX types (char2, 4, 8, 16) are not well supported. They are
>> likely to disappear in the next release, with the parser mapping them to
>> char(X) (or varchar(X), whichever is the best match) for backward
>> compatibility.
>>
>> The major string types are char(), varchar(), and text.
> Is there a performance hit if the values chosen are not powers of 2?
No, the smaller the better.
Andreas
