There has been quite a bit of discussion about which versions to offer, and what should be included in them. This is good, at least it is covering the intended topic!

Some of the better players have contended that the '13' variants should not be offered, or if they are it should be with the movement restriction of the first player's second turn. I disagree. Pente13 and Keryo13 (unrestricted) are very playable and enjoyable game concepts, even if they are not quite what the original inventor intended or lack the professional draw of the 19 board versions.

It has also been stated (by Dmitri, I believe) that playing the 13 versions without the move restrictions spoils players who might later become serious about the 19 versions. I disagree here also. Learning the professional movement restriction is not hard at all, and any player should find this an easy adaptation. The hard part is learning to play well!