Hello Mike,
I think I understand your concerns.
First of all it is important that you understand how to measure the nose load, as twin axels are more sensitive to hitch height than single axle caravans. The suspension units of both axles interact in such a way that a change in hitch height makes a bigger difference than would be the case for a single axle unit, so attention to detail here may prevent unnecessary worry.
Briefly,
The whole caravan must be on a horizontal surface.
The hitch must be at the same height as your tow hitch when it is connected to your car. And the nose load must be measured vertically from the hitch it self
You are correct to wish to avoid placing heavy items at the extreme rear. This can exaggerate stability issues, but often it is only necessary to move a few Kg to bring the nose load into range.
Carefully consider what items you carry in the front gas bottle locker, The gas bottles must be there for safety, but what about the electric hook up cable, or the wheel ramps, cricket bat etc, these items can add up to 10kg, so simply taking them out of the locker will reduce the nose load, and if these are then stowed towards the rear of the caravan, they will actually further reduce the nose load.
If only 10 to 20 Kg of mass added to the rear of the caravan causes the outfit to become unstable, then you have much bigger problems than just nose load.
Fortunately, twin axle trailers are generally considered to be easer and more tolerant to load than singles so rather than worry about unladen nose loads, load it up and play with it until it you get the way you want it.