Alejandro,
I have used Shureido's wall mounted maki and found it quite effective IF used properly. Understand that contrary to popular belief, there are a variety of different types of makiwara used for reasons other than just conditioning the hands. Even the traditional floor mounted ones can vary, depending upon the wood used, the tapering , and the way it is mounted. Some are designed to have a quite a bit of give in them for more intensive focus strike drills, while others have less give and/or a more intence spring back on them. This second type tends to put more stress on the wrist, elbow and should joints and if not used properly can cause you serious injury. If you choose to use the wall maki, please keep this in mind and use it with care, using medium range power strikes.
This said, I can tell you that shureido's maki is well constructed and holds up to quite a bit of punishment (I havn't always followed my own advice and paid the price.) If you do purchase the maki, and plan on using it on a regular basis, you might want to order an extra wood plate to have on hand for the occasional breakage that occurs. Hope this helps.
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All streams flow to the sea because it is lower than they are. Humility gives it its power.