Many researchers routinely use HEK293 cells at 1L scales in 3L shake flasks and at even larger volumes in 10L or 20L Wave bags or benchtop bioreactors. Certainly CHO cells can also be scaled up, as the vast majority of biotherapuetics are made in CHO cells at multi thousand-liter scales. Scaling up transient systems from mLs to liters is not trivial, and some cells will scale up better than others. When scaling up the dynamics in the shake flasks can vary considerably and one has to consider shake speeds, gas exchange, baffled vs. non-baffled flasks and temperature among other variables. At this time, I would recommend the use of HEK293 cells, as the yields from these cells tend to be considerably higher than CHO. Once again, the Expi293 system has been validated to generated consistent titers from multiwell plates all the way up to 10L Wave bags.