Hi John,
If you look at Ksor's pictures you'll see that his location pins are halved such that the centre lines correspond with the edge of the bar.
If you use round location pins only the centre line hole will work accurately as this is independent of pin diameter. If you want to divide by e.g. 4 on different size bars it's not reliable. The smaller the pins you use the more accurate the division.
The following two pictures illustrate the problem:
![](http://listerengine.com/coppermine/albums/userpics/10017/CenteringTool100_zps6f24abf6.jpg)
![](http://listerengine.com/coppermine/albums/userpics/10017/CenteringTool80_zpsa71710b7.jpg)
You'll have to tell people that the extra holes are to lighten it!
Cheers.
Phil.