Although I have heard some suggest that Low Iron Glass has a lower Tensile Strength then simple clear, none of my own tests have confirmed this. In any event, due to the variability of the strength in any annealed glass product, I always design to remain below the stress value which was induced during the toughening process - i.e. if you specify a toughening compressive stress of 70 N/mm2 then stay below that value (with a safety factor if you wish) and you know that you are safe. If you adopt this design approach then any slight reduction in tensile strength of Low Iron glass becomes irrelevant.
That's how I deal with it anyway!
Tim