My car bra helps, they usually look at it and decide its just too much hassle waiting for me to take it off.
I think staying cool, no mouthing off and your age helps as well. I've been pulled over for RBT heaps of times but that is it. I was even chased for an RBT once and no problems. I passed the RBT site and they didn't wave me in so I kept going. They chased me and pulled me over about 20km up the highway.......I was doing my 100kmh, I guess it took them a while to get to their car and get going etc and I have no idea what speed they did to catch me. They had no issues with me, the officer admitted that they didn't wave me in, but they must have changed their mind after I went past.
I've never had to pop the bonnet, but even if I did I'd be OK unless they dug deeper or really knew their stuff - low mount HKS with a 3076 deep down, the bonnet is no problem.