Gday Richard i have had your problem of sagging lop sided springs on our 09 16 ft we came back from a trip up north , jacked the van up to do bearings and the r/h/s spring fell apart at the eye. I have no faith in alco springs now so i went to a place in Adelaide called Industrial Springs where they sold me a 10 leaf complete kit of springs/ hangers,pins / bushes / bolts/nuts for $480 . Fitted it all up and tows like a dream no more sloppyness .
Hope this helps
cheers Russell