[rich2202]

Are you talking:

1) in the pit/que right before a match?
2) At a FRC event, other than right before a match?
3) Outside of an event?

#1 is not possible.
#3 anything goes.
#2 is the tricky question.

For #2, I would make a removable air tank pack that can fit into/onto your robot. It should have 2 connections:
1) Connection to robot vent valve
2) Its own vent valve

During practice, you can run with however much weight you want. While you are in que, you can tether and charge all the tanks you want. Or, even bring the robot charged to the practice field.

For competition, you can remove the extra air tanks.

IF you can get the LRI to allow you to run 2 compressors off field, the removable air tank pack could have a 2nd compressor mounted to it (with all the safety stuff). You would then need a connection to a second PCM, to power the 2nd compressor.

Note: At the championship, I forgot if you had to pass inspection in order to use the practice fields. If so, then you can only run on the championship practice fields in competition configuration (without the spare air tanks). However, there were practice areas where I think you don't need to have passed inspection.