https://www.hobie.com/forums/viewtopic.php?f=78&t=46320
Or plenty of other content/examples on hobie's forum page.
I used to have this setup on my PA 14. Helps to have another hand, if possible to set the tubes to the correct placement under the hull. Be sure to set the height at or slightly above the truck bed's height. I drilled a couple holes with a spade bit into the PVC first, this allows you to fasten some lag bolts and washers. You can also use some "L" brackets to help support the PVC and help with placing.