I've rethought mine as well. Was gonna go 4x4x4 but then the middle row of wood in em would take a LONG time to dry out, instead will be building them 4 foot high, by 36" wide and around 5 1/2 foot long which will still give me half a cord per rack.
Got to looking around and have come up with a bunch of 2 1/2 OD pipe with 1/4" walls, also have some channel irons that were the tracks for the trolleys on a couple of augers that overturned. I'll use the channels on the end for uprights.