These are the rules that PBP checkers will be applying:
"[Tribars/clip-ons] sont autorisés à condition qu'ils ne puissent pas dépasser la ligne passant par les points les plus en avant des poignées de frein."
"Poignées" are the brake 'handles' not the levers (leviers). So I reckon @Vorsprung's drawn line is pertinent.
But triathlon draft-legal rules (English version), from which presumably the ACP decision/reglement has been derived says "Clip-ons, including the bridge, must not exceed the foremost line of the brake levers."
Anyway, in the spirit of "une ergonomie améliorée", what's a few mm between friends?
Bonne chance à tous.