Footings and steel piers for Transportable.. help

Hi all,
Does anyone have info on footings and steel piers to support a Transportable or link to were I should be ?? thanks

Being a new OB I am having trouble (confused) with plans to suit B.A. NSW to suit a Transportable.
To go on a level block, soil test done..

The Transportable is 15 x 6 in two halves, it has a 6 piece I beam sub-frame and timber frame dwelling attached.

The Eng plans show 54 pier holes 450 x 600 deep but with cement just 200mm deep ??

Also seemingly super heavyweight metal piers: 76 x 4.5 CHS (pipe)
?? : I have 50 x 7 CHS ( already owned I wish to use).

And cross beam on top of the piers.. 75x75 x 5 SHS
?? : Why would this beam be needed at all ?

Summary: I have 7mm thick 50mm dia steel pipe that I wanted to use for piers.
Also I don't see the need for a cross beam on top of piers.. ??
except to make landing the unit by crane easier.

Is 200mm of cement at the base of 600mm borehole enough, with 400mm of dirt infill ?? Maybe it is ??
Or should the entire borehole be filled with cement 450 x 600 deep.

And the 200mm act as a footing for the pier to sit on
prior to cement OR dirt? in-fill.

Also: What is 'FOUNDING'.. as in founding notes on the 'plans'
Is it another word for 'footing'..

So confusing..

Yes, I will contact the Engineer again..
However, I would like some info to go on..
Thanks, Forum..

Am in the Riverina region.
Thanks. Over