Need your advice, sorry, another woodshead post.

From you pics, it looks to me like you should put at least a 2x8 at the front, and back, under the floor joists and perpendicular. Bolt these to the existing 4x4's. I would have also put one in the midde, but you currently don't have footings there.

I'm with bogydave on this one. Take out the floor, use pallets and take all the worry out of it. If you want to level it, put more pallets on one side than the other.

Crisis averted 2 rows of double 2 x 6 laminated together and running perpendicular to the floor joist. Used bottle jacks and installed 2 extra deck blocks with 4 x 4 up to the 2 x 6 connected with strong ties. Also manged to use the bottle jacks to raise it up and put footings ( 4 x 4's down to concrete blocks) down the center. A few more little things to do and wood splitting and stacking will commence. Thanks for all the advice. Will post pics when it full.

I would leave the front and back open. You'll get more wind that way, and it will be easier to load and unload wood without the cover on the front.

I have the same concerns about the floor strength that others have described.

I was happy with my outside, uncovered wood stacks this winter, but in a snowy winter I'll be wishing I were you.