"Was there any other reason you chose this arbitrary barrier cutoff besides to show agreement with your computational approach?"
No. As we write two paragraphs further down: "We note that defining the cutoff is done purely for a post hoc comparison of experimental and computed data. When using the computed barriers to identify promising experimental mutants, one simply chooses the N mutants with the lowest barriers, where N is the number of mutants affordable to do experimentally (e.g., 20 in the discussion of set L)"
"I can't seem to find a plot of experimental vs. computationally determined barrier heights, which would be very valuable to a reader, I am just missing it?"
As we write in the preceding paragraph: "Given the approximations introduced to make the method sufficiently efficient, it is noted that the intent of the method is not a quantitative ranking of the reaction barriers, but to identify promising mutants for, and to eliminate non-promising mutants from, experimental consideration. Therefore only qualitative changes in overall activity are considered, which are represented by the activity factors ( + 1/−1)"
Furthermore, the experimental activity assay data reflects more than kcatand can not be directly, quantitatively linked to a barrier.