Tool strip with locating holeToolstrips need space too!
Often lately I see tool strips reduced to the point of frustration for machine operators. I have often retracted the rails on a Mydata Assembly machine beyond their proper position just to be able to use the fiducials. This creates upward bending of the panel and other problems. Transport widths of various machines are opened beyond normal in the hopes of being able to see fiducial marks. This may work in some cases as long as the PCBs do not fall from the transport. This comes back to the rule...

Leave 5mm between the outermost edge of fiducials and board edges!

Given this the minimum width of a tool strip should be 5mm plus the width of the fiducial plus a small border to the inside edge of the tool strip. This would give a minimum width of approximately 8 mm for a tool strip.
Holes in the tool strips for mechanical locating and fixing of the panel or PCB are often 2.4mm or 3.2mm. These can be centered in the width of the strip but fiducials can be easily shifted toward the inside edge of the strip further reducing the shadowing effects possible by transport rails.