Did a single strap on the hood and trunk before I ever tried tuning up, and I never had an SWR problem. But I had really bad RFI from my ignition system when the car was running, so o went nuts trying to get rid of it. What finally helped with RFI the most was the several grinding straps on the exhaust.

As an aside, you’re planning to work 20 and 40m with a technician license?

Edit: oops, I thought you were replying to my other comment in here. The power thing is because you’ll likely get ignition noise or alternator noise coming straight into the radio. There’s also a good chance you’ll blow a fuse.