Ondai, sorry nobody has answered your post, though maybe thats an answer in itself.. However my experiance with Zen putters was at th Faro shopping centre on the Algarve, they had a exhibition going on there with pros showing you how to putt, they were quiet so I had half an hour with them I found it fascinating but no matter how I tried I couldnt get both balls in the hole I also found that I was concentrating so much on my stroke that line and length went out the window. these things are OK but you need to wield them in the heat of battle to find out how they behave,, Good Luck..
