Load distribution concrete mixer semitrailer

I plan to buy a concrete mixer semi, the trailer have 3 axles and a 13m3 capacity.

I try to figure out if i can legally load 12m3 and get close to 50tonnes which is the limit here in norway. The trailer have a 24ton capacity on the axles according to regulation.
The tractor have the following limits:
Steer: 8500
Drive: 11500
freewheel: 9000

How can i figure out what axle configuration is beneficial for the tractor? and how do i establish the placement of the 5th wheel.

I could figure this out by weighing and i will probably do, but before deciding what to buy im doing investigations.

Thank you vey much