I made one just like it and it works great. It probably cost me $25 and is well worth it. I don't care what anyone says, if the forks are on the bike there is no way to ensure the oil level is exact. If you take out six ounces and put six ounces in how do you know the oil level was correct when you started? You are just making an assumption unless you take the forks off and do them by the book. When you take them off, this is a very good clamp to use to hold them.
I used an old lower tree, cut it off just after the pinch bolt hole, spent a few minutes at the grinder to clean it up. I know its the perfect size and holds tighter than ANYTHING lined with rubber ever will!