[BillA]

Les
there is absolutely no reason that I am aware of that necessitates an apology from you

no, "key to chiller performance" is the attainable die temp at load
to me the actual cold side coolant temp is not the measure of performance

here is some grist for the mill:
2 250mm² TECs @ 226W (presumably Q max ?, V max and I max not known)
- @12.0VDC drawing 16.7A each
hot side coolant held @ 35.0°C with a flow rate of 340lph
cold loop using 25% antifreeze, no insulation on lines or wb - and LOTS of condensation
heat load applied through 100mm² heat die and a MCW5000 rev2 wb

some results:
Watts . coolant . die
39.4 ..... -1.9 ..... 8.1
49.8 ..... -1.0 ... 10.9
59.6 ...... 0.4 .... 14.1
69.9 ...... 1.8 .... 17.6
79.6 ...... 3.3 .... 21.2

steady state assumed, but may not be absolutely correct

can Kryrotherm back calculate the cold loop flow rate ?

g_f
that is what it looks like if the outside items are wbs
yes, the 1/4" barb is one side of the 'chillin' chamber'