Cinder blocks are safe if stacked correctly. Start on level ground, set two side by side with the webs vertical. Stack two more on top the opposite direction, webs vertical. Now cap with a solid piece of 2x12 running running perpendicular to the top two blocks. You effectively have a 16"x16"x16" pilaster.
I like the cribbing idea with the 6x6 as well. /\
