the comprehensive rule book states that a character game text box is blank whilst stunned, however it does not clarify which characteristics it keeps.

ive always played it that a stunned character still has its name, affiliation and cost, but do they also have there atk and def, flight/range, concealed, version etc?

The only things that are lost when stunned:

1) Text box contents (exception: Concealed and Concealed-Optional now exist outside the text box, even for older characters who had it as a keyword)
2) Attacker, Team Attacker, and Defender characteristics
3) Cosmic counters

In return, they gain the characteristics "stunned" and "exhausted".

Nothing else changes.

coolio, cheers spud