Surround the PVC with slip on urethane insulation sleeves. At each support joist fasten an appropriately sized O-ring to the PVC with an automotive hose clamp. Slightly tension the O-ring and fasten to the joist with an industrial wiring staple. As a safety, loosely attach a loop of mechanics wire through the staple and hose clamp...

I have seen o-rings used on Volvos as exhaust system hangers and think this might work.

kind of similar to another idea i had which was to get a bunch of these solid rubber bungees and loop them around the pipe, remove the hooks and screw them into the sides of the joists through the hook holes allowing the pipe to hang down into the crawl space

...I would still add the slip on insulation for the extra dampening.