So basically 3 European men or 2 Americans.
Any possibility to fold the seats and put a 1/2" plywood to shift the load more towards rear seat?
The car has a payload of about 850 lb +/-50 lb.
You and whatever equipment/luggage you would carry plus the load is still within the range.
Hence spreading the load more towards the center of the car I feel will be much better option and overall cheaper and easier than messing up with suspension.
In addition, keeping the extra weight in the very rear of the car will cause a lot of stress if you need to suddenly turn.