for regular go-moku (which this is essentially the same) i have never played on a board bigger than 13x13. They use that at IYT...i have played approximately 200 games of that and 2 of them have filled up, both agaginst the same person (lol). 15x15 would certainly be big enough though imo!
(do skréše) Vlitni do špilo v to rano! Při vepoštěni taho si aj se sópeřem namontojte "táhnót a pobét toť" a furt dokola oževojte léstek bóchánim do klávese F5! (TeamBundy) (okázat šecke vechetávke)