Only downside to having flexwatt ran in one long piece or all wired together from shelf to shelf, is you not put the entire rack in risk.
If one shelf malfunctions the entire rack malfunctions, And then you have entire rack to replace worth of flexwatt.
When I wire up a rack I use 6ft cords cut to length to minimize long cords, Each shelf is soldered to its own plug. This way if something isnt working right or stops working, I can pin point the problem fast, and fix it fast without having to redo the entire rack.
I number everything, The power strips number is which rack its powering, And numbers on the cords, represent which shelf its powering. And then each plug has a smaller number indicating which surge protector it goes to, to make sure its plugged in right power strip. I always use power strips with Light indicator that its powered on.
In the picture each powerstrip is powering only 57 watts of flexwatt. coming to 8 watts per plug. Doing this you will never stress the wires enough to ever have a problem with fire so long as your soldered connections are dont correctly.