There shouldn't be much of a concern here....
There are many factors that would affect the performance of CRs... other than sizings...
issues, like quality of media, whether the CO2 tubings are leakproof etc does contribute to slight variance in results... (Hmmm, regarding this.... was wondering whether the grade of CO2 does give different results..??)
Not to forget that Weileong's unit runs on a eheim 1250... therefore resulting in more water flow and also his recently acquired CO2 precision control valve ...... (better control)
I have received readings from the other reefers ... both large and small units....Readings so far have been pretty close to what you guys have been getting.....
You don't have to lose sleep over this...