Cascading Wings: Do they really increase lift by 300%? Cascading Wings for Ultralights: Do they really increase lift by 333%?!?!?

The classic NACA 650-18 airfoil has a Clmax of 1.5 according to airfoiltools.com ( a modified 650-18 is used on the Zenith 701).

Add non-slatted flaps, and the Clmax jumps to about 2.2.

What if one arranges the wing in a cascading fashion as shown below? Javafoil shows the Clmax jumping to 5, that’s an increase of 333% over the plain wing!!!

Not by just adding the same planform, but dividing the original chord by 4, so the a/r ratio is 4 times the original....

So that the quadplane is 400% more efficient than the original monowing, less a quadplane inefficiency of about 50%, so that the quadplane is still 200% more efficient than the monowing(maybe).

This probably only works ( if at all ) for very slow speeds (Re 300-800k) where the form drag and induced drag is very low.

I understand Javafoil uses Xfoil, which I’m told is a robust airfoil performance prediction program and is accurate up to an AOA of +/-20 deg.

Alternately, I’m told the VLM method (XLFR) is good up to only a Clmax of 1.5, +/- 20 deg.

So…. the million dollar question is… is a Clmax of 5 realistic, or is this beyond the scope of Javafoil/xfoil, even though the AOA is only about 8 deg….?

Ultralight Design Data: 

See charts and tables below.

Flaps: 20% chord, 50 deg deflection

Wing Loading:51kg/m>2

Aspect Ratio: 7

Atmospheric conditions: Standard

Wing configuration: see chart below

Gap(vertical): 50%

Stagger(horizontal): -10% 

Therefore biplane ( not multiplane) lift efficiency as per the table below should be: .26/.34=76% efficiency vs mono wing (Is this correct?) ( ignore the big green arrow, it's from the source I found the table)

Reynolds #: 880k

or......

is there a glitch in the software as per the comment below:

and the Clmax is about: climax 5 / 4 wings = 1.25

given the Clmax for a monowing is 2.2, and a biplane at 50% gap is 22% less efficient, a quadplane with 4 wings can easily be 40-50% less efficient, giving a clmax of about 1.3, which is close to the clmax of 1.25 above.

So what is the likely Clmax, 5 or 1.25?
The software appears to be taking the net plan area or shadow area of the overlapping stack as its area, but is adding the individual lifts of each wing. If you add the individual areas too then the calculation should show a fall in Clmax due to interplane losses.
I'd call it a bug, however I do not know the software so perhaps it is a "feature". It depends on whether you regard your stack as one wing or four.