Someone should look through some IYT Keryo pente games and find examples of games that were won by player 2 as a result of player 1 not being able to use the edge due to the smaller 13X13 board.

See, it is very difficult for me to prove that there is limitation of player 1's advantage, but, it CAN be shown, by example, that it does reduce P1's advantage if some examples are found.

On a non-serious note-- how about pente on a 5X5 board? I bet that would SIGNIFICANTLY reduce the frequency of wins by player 1!