Every cleanroom user should remember that any designer, design the system by considering minimum 10% of safety. If end user, while providing the load data add his percentages of safety, then it multiplies to infinity.
Knowing your system is the best way to avoid the need to oversize, whereas studying and understanding process needs narrows the margin for errors.
Studying and understanding process needs, & assessing the reserve capacities among the system is really a big challenge to the TAB & CPT professional.
Curtailing OR Tuning the system to the desire should be the ultimate solution.