Jerry, the safest way is to stack the blocks so the wood grain is horizontal (running parallel to ground). Wood splits easiest in the direction of the grain (think splitting logs with an ax).
In the case of those PT 6x6s I doubt you would have a problem either way you set the blocks.
Regarding letting the weight down - do you need to rest the body on the blocks to take "pressure off" the hydraulics for your repair work? If not, and the blocks are within a inch or two of filling the space, I would not worry about it. The blocks, in that case, are just there in case the hydraulics leak or blow out.
I thought you were up in the mountains to relax.