Hello avaiojet,

This topic of including or not including the fuselage in the lift area has been discussed in the past adinfinitum.

As I recall there was no definite conclusion reached.
The thead became one of "forum politics" more than analytical.

Some judgment has to be used based on the type of fuselage involved.
If the width of the fuselage is less than 10 to 12% I do not include its width in the wing span as one factor of calculating the wing area.

If the fuselage width is more than 12% but less than 25% I tend to calculate using both meaning with and withouot the fuselage width and compare the difference. It is often difficult to figure out if the fuselage has an appreciable lift factor. It can be either way versus the main wings.

When considering a "delta wing design" which, most of the time has a high leading edge sweptback I include the fuselage as part of the lifting surfaces. That seem to be realistic and make sense to me.
I try to evaluate the contribution of the fuselage part of the lift forces.

These days the power to weight ratio is more important than the wing loading.
Nearly all modelers equip their model with an engine/prop assembly that provides moe thrust than the the model weigh.

It is easy enough to calculate both ways using your posted figure.
I suppose that by "fuselage thickness" you mean the width of the fuselage in the wingspan direction.
When including the fuse in the area I would consider the chord of the wing to be the same as the root across the fuse.

Zor