[alarie]

We run 2 compressors in my shop and there are no problems doing what you suggest. We have a 7.5 HP and 15 HP hooked together, so we have a backup if necessary, but they are both on line and both motors run when demand is high (sometimes 4 air sanders running). As noted by others, the extra tank capacity will help, stage the motors so they come on at different pressures, and let it rip. We have them hard connected, but they are bolted to the floor. Keep the hoses big for connection if you do it that way.

I agree that if you really want to sand/grind, you need 80 gal and at least 7.5 HP to push it.

Good luck, but you should have no problems.
Peter