Intex makes a vacuum hose adapter that hooks up to your suction port.
If your suction inlet looks like this
Then buy this adapter
Intex Surface Skimmer Wall Mount Hose Adapter https://www.amazon.com/dp/B0050KAGOU/ref=cm_sw_r_cp_tai_uSqVzb3YMVVT3
It's still wobbly. I have water in the outside legs and have ratchet straps down to the bottom legs as well. There are some other modifications I may try this weekend. I don't think it will ever be rigid on this style pool because the walls are supposed to float back and forth.
just filled mine. i placed a 12x24 foam on the ground. my legs only moved about 6" total from the edge of foam. drawing shows 11" on center. but mine only moved 6"