Shortbread with a snap I would like my shortbread to have more of a "crunch" snap to it; to also allow it to travel and not get damaged.

Is it too obvious to say cook for longer, or do I need to add more flour?
My recipe is as follows:  1034g flour, 924g butter, 462g caster sugar and 264g corn startch.  Oven temp 150 for 45min.  I am then cutting them into fingers.
Your recipe is a bit short of flour for a classic 3:2:1 flour:butter:sugar ratio, counting both the flour and cornstarch with the flour. You have 1298 grams of flour and cornstarch combined, it needs to be closer to 1386. A bit more flour will certainly help, but your method should also be considered. I would recommend cutting the butter in rather than mixing in order to deliver the best crunch. 

Last, if you're cutting them into fingers then it sounds like it's pretty thick. I've found it's hard to get thick shortbread to be crunchy without overcooking it, I'd suggest thinner is better. 

When baking use the touch test to detect when it's ready, you want to bake it until it firms up some, a few test batches will give you an idea when it's reached the point.