Storing Arctic Fox 990 for winter

You are in snow and snow sitting on any camper can be an issue. I keep mine in my garage on a boat trailer I set up for the camper.

I guess if you have kept up on seal maintenance you'll be ok but if you haven't, letting it sit out in the weather is asking for trouble.

Has to be outside just worried about sitting on grass even though I’m putting boards under jacks

You will be fine. Keep mine outside and do the same thing.

If you are going to put the cinder blocks in the corners of the basement I would get a 1/2 or 3/4 two by six and place it across the width of the basement to distribute the weight.

Just putting cinder blocks in the corners may over stress those areas of the basement. You want to distribute the weight..

I don't need to winterize my campers where I have them, but I always put support under front wall when off the truck. That is where the most of the weight sits and helps to stabilize the camper when in use.
I had to rebuild front, lower wall on Fleetwood and not visible to bare eye, the front sides sag over the years by well over 1".
Now when I set the camper for longer sitting, I grab a level and adjust the front support and jacks to keep it square.

Just take it to sidecars house and store it there in his barn....
No it won't hurt and for sidecars sake......they make these things called, wait for it, covers and tarps! Weird I know, but they can be used to protect things like campers from the elements.

Whether you need 2'x2' pads is a function of soil and moisture and the propensity for it to sink. If you're also supporting with cinder blocks and boards, 2x2 pads seem large for the jacks if they're ultimately not taking much of the load.

Don't need to support anything under an AF camper. They'll hold fine on the jacks, even while in use.

I think as long as you have a stable foundation under each jack you will be fine. My AF 990 sits outside year round sometimes on the truck & sometimes off, although mine is on cement. I never put anything under the corners of the camper to support it, I let the jacks do the work, been doing that on my two campers for 14 years & never had a problem.

Big Rig

I’m going to use 4X6 across each set of cinder block.