Sandbags in pickup bed, placement?

to me it makes sense to put the weight in the bed, toward the cab, to center the weight,, works for me anyway...
what I do is towards the end of November I go to the local Lowes and get six 40 lb bags of top soil,, stack those in the bed, towards the cab end,, they lay flat, don't slide around,, next spring,, the wife always wants to re do some flower pots, or I put the soil on the garden,,use it up some where..