TenGo

In this Go variant, a player's score is the number of stones of their color in a group that includes a stone at tengen, plus a komi in the case of White. On their first turn, Black places a stone anywhere (or nowhere) and chooses the value of komi. Then, the second player chooses sides. Komi must be of the form n + 0.5, where n is an integer (... -2, -1, 0, 1, 2...).

Open questions: What is the right value of komi? Is there any board size where Black can win with a first move other than tengen and a positive komi? Or, what is the same: is there any board size where Black can kill a White group at tengen?