Andy & all,
I don't want to embarrass anyone; but I would hate it more if someone got hurt and nobody said anything.
The wood blocks for the jack to hold the gear look great. Makes a nice recess to hold the top of the jack and keep it from sliding.
Take a look at the orientation of the cement blocks - with the cement blocks on their sides. Cement blocks have very little strength on their sides - if using cement blocks for this purpose - put them top side up and put a 2 X 10 under the jack - better yet - stick to wood blocks. Cement has tremendous compression strength - very little tensile strength - on their sides the blocks can easily be placed under tension between the webs and crush under very little weight.
They guys who do hand chops to break cement blocks and impress the rest of us hit them on the sides - the weak point between the web - never see them karate chopping a cement block from the top.
No offense - just don't want anyone getting hurt.
Sincerely,
Dave S