Hi Ebar44 ,
I think your problem with the Little Giant was pump cavitation see this link http://www.mcnallyinstitute.com/01-html/1-3.html With a steady flow of water/coolant your condenser will work at its maximum but if your cooling water has air bubbles in the stream you will not get maximum cooling
Now if you couple this with lowered pump head (i.e. how high the pump will pump the water) caused by low pump intake pressure the water volume and flow will be greatly reduced on what seems to me to be marginal head pump for the job i.e. the Little Giant and this will cause bad heat transfer.
If as you say in your post the Flowtec waterfall pump has rated connection right down to 7/16 you can rest assured the manufacturer will have tested inlet pipe sizes down to this size and sized and rated the pump accordingly so that cavitation doesnt occur with this pipe size.
Hence you can be reasonably certain you will have a smooth steady bubble free water flow(minus the bubbles) through you condenser. This will mean an all round better condensing run, i.e. a quicker distillate collection than your usual run for, fore shots, heads, hearts and tails. And as you can verify a steadier run i.e. a rock steady 78.1C hearts collection rate and an all round better temperature maintenance through-out the run.
What you have drawn to everyones attention is you shouldnt under size a centrifugal water pump or cavitations occur on the low pressure side of the pump in other words dont send a boy (i.e. the little Giant pump) to do a mans work (i.e. the Flowtec)
Cavitation is rarely taken in to account when thinking of head pressures for their use in the public arena because it is seldom understood