Home Depot Man to the rescue!
it doesn't matter weather you use steel grating or wood. 99.9% of the weight is carried by the beams. The weight carring capacity is based on how thick the beams are from top to bottom. 4" thick are rated to 10,000lb's on an 8' span by the manufacturer that made our racks.
The pallets do not even need the lumber or metal grating. That is just to keep the product from falling through the rack if it comes un-shrinked or for the forklift driver who doesn't know what he is doing.
besides, you are laying the 2x6's flat. They would deflect beyond alowable with me standing on them. (alowable is usually length/360)
<--- was forklift trainer for Home Depot for 3 years.
If you don't believe me, get a 1/4 pallet of rebar. This pallet is suppoed to be put on the floor in allinstances because it weighs about 4000 lbs, but will not span the racking. It will snap the 2x6's like twigs, and will bend the metal grating to the point it taco's and falls through the rack.