To jack it up, I put the floor jack under the subframe tubes. To support it for pulling the subfame off, what I normally do is use a pair of jack stands with small 2"x4" blocks of wood. Then place the stands/wood under the running boards below the foot wells.
You may have to "add some ballist" to the rear of the sled to keep the front end up, until the skis are off!
HTH
Bill