Research what types of speed detection units are being used in the area you drive in. If it's still radar-only, something like a Valentine One does a great job but it's still advisable not to do more than 5mph over. We work on a lot of cop cars and there are a few benefits (PBA cards are nice) but I do get to pick their brain a bit. Most of the guys sitting in the speed traps are waiting for a 13mph+. It's easier when you pull someone over because they are clearly wrong and they know it, it's not as much drama with some crybaby story. Those leave a lot more room for talking down in court, and, the bottom line is, they are bigger $$$ tickets. Some will go for people even 6+, but it's time dependent. Big road with a lot of cars out, they'll wait on a big one. Small road late at night with only a few cars here and there, it takes less to get a ticket.
If they are using laser in your area, and most are now, fuzzbusters are completely useless. There is no way to pick them up before you're shot. The top brands like the V1 that guarantees they will pay your ticket in the fine print say radar only. Tickets are checked at the bottom what was used. And they don't pay the insurance hikes, the points, etc. that follow you for years.
Best bet is to set the cruise at 4 over. A college class mate did a speeding project for his statistics and physics majors and came to the conclusion that unless you are on a freeway with no traffic lights, light traffic, and you're on a drive of 3+ hours, you really gain just seconds by doing 15+ the speed limit versus going the speed limit. It has a lot to do with the timing of lights. You can get a half mile ahead of someone doing the speed limit over the course of ten minutes or so and one traffic light or one person driving slow in the left lane and all of a sudden they're right on your ass again, and they didn't risk a $400 ticket and 4 points the entire time.