As every good engineer knows, the strength of a beam is related to its thickness, not its width.  So said my father in law Pat Todkill when I consulted him regarding having slats cut for an antique wooden bed.  We settled on maple 1 by 6s from Adams & Kennedy, a local lumberyard. https://wood-source.com/company/ Adams & Kennedy allowed you to have your boards cut once for free, but Pat ran them on his table saw, because I didn't have the dimensions handy when I was at the lumber yard.