V this is how we level our twin axle.
First you need the large Fiamma yellow blocks
(2) measure the distance between the centre of first axle and the second
(3) remember this meaurement and place yellow fiamma blocks back to back on ground, now that measurement you took ,you need to space the blocks that far apart.
(4) you can either drive onto the blocks or reeverse onto them ,found it best to drive on .
(4) now you can level your van front to back using the jockey wheel not the legs these are only to stabilise the van.
Good Luck .
Sir Roger