Ross, 6 MPH for any sizable power boat would propogate a pretty substantial wake. To really eliminate a wake from a power boat you would be less than 1 MPH which really gets tedious. I've noted that with my ski boat, which weighs less than half my sailboat, the wake at a low speed of about 5 knots is pretty substantial due to the hull design; whereas, the wake from my sailboat at 5 knots is barely noticeable. But at 30 MPH or more, the wake from the ski boat is very small (even smaller yet as you increase speed to over 40 MPH).
Tommays, when I stop my ski boat rapidly from a plane to sub-planing without changing direction, it does send a wake forward that is pretty good sized. The technique that water skiers use with a tournament style inboard ski boat (Ski Nautique, Mastercraft, Malibu Skier, etc) when a skier goes down is to make a sharp full speed turn while simultaneously reducing the throttle to idle. When you do this correctly at 36 MPH for a slalom skier or 40+ for a barefooter, the small rudder breaks loose from the water and the boat spins flat, in place like its on a turntable and comes to rest with the bow pointing in the opposite direction toward the skier. Then you simply idle over to pick him up and you've done everybody a favor by leaving no wake for anybody to contend with. You can't have anybody sitting near the stern of the boat because they could be launched into the water.
If I did this in front of the State Police, I would get a ticket for sure, and possibly be towed back to the barracks for arrest!