From the VEX-U Appendix, the rules allow for any commercial storage tanks, and give no limit on size or number, just the 100 psi limit:
<VUR10> Teams may utilize commercially available pneumatic components from the following list: Cylinders, actuators, valves, gauges, storage tanks, regulators, manifolds, and solenoids.
However, the newly released robot inspection checklist, VEX Parts Inspection point 20, specifies VEX air reservoirs and limits it to two, in conflict with the rules stated in VUR10.
http://link.roboticseducation.org/vexu_inspectionchecklist201819
Please clarify which rule is correct, and correct the incorrect one. Thanks!