I had some time during the Christmas holidays, so Ive built my own measuring tool which will hopefully save me some time in future. See photos at http://doublebassguide.com/?p=1007 The shaft is a aluminum tube of 10 mm diameter. On one end, I glued on a steel ball with epoxy. On the other side, I inserted a brass thread and a screw (M8) for length adjustment, again with a steel ball glued on. Then, I put magnet rings on both steel balls. The power of magnetism holds them firmly on the balls, but will allow the to follow the curvature and angle of back and top smoothly thats the key idea of this device. With some sandpaper, Ive dulled the balls surface, in order to prevent the magnets from moving too easily. I now set the device to the guessed length of the upcoming soundpost, set it into position inside the bass and re-adjust the length if needed. The magnets are much slippier than soundpost wood is, so I glued on fine sandpaper. Once the device has the proper length at the correct position, I remove the device carefully (so that the magnets stay in their position). For inserting and extracting the device, I use a fixed bent wire instead of the S-shaped soundpost setter tool but this still needs some improvement. Besides this, its pretty cool. Transfering the angles to the soundpost is still a little tricky, but much better than guesswork.