[Les]

All looks sweet after all.
Made some wholesale cock-up some where.
First graph crap.
Not even know where offending curve came from.
Only data on work sheet resembling is your "System C/W".
Have recalculated nothing.
.
Ratio 1.038069429 is way out.
Horse lost.
Not been my day.
Ta for extra Excel.

With the amount of data you produce even I am considering some magic.
Thinking of LMTD ?

Morning Edit . Added Series3. Every thing behaving.
Retaining "L=2.23......" in picture .

Effect on predictions of moving "Shadow Model" zero to the, possibly more realistic, wb/Fluxbloc interface ? Having a look-see.

Lunch update
Not sure whether needs Fermi to have another crack at it.
Not sure is better.
Not sure ............
Though, is food for thought
Manually getting Ts and Ls is a chore and my magic is very limited