I agree that the size is probably good. (I thought it was too big at first.)
I think 8x8 would really be too small.. Maybe 10x10 would still be good. But I actually like the 12x12...
18x18 would be WAY too long!..

I would like to read about people's strategies.. Because it seems to me, there has to be strategies more complicated than my own. Mine seems rather simple. (Not sure if it works yet, as I haven't completely finished a game yet! lol)