Kyle, it wasn't me that gave you the tip.
Holdfast, the straight and Blackstone are heavily fished and have alot of boating pressure. You will have much more luck going off the beaten path and fishing areas that have much less boat traffic.
Nofish, Musky or Specks is right that Port Rawson is a great place to camp and should be really private in May. The cruisers aren't out yet but the Blackflies might be! The only downside is that the distance is almost 7 miles, so if you have a small boat that is loaded down with gear, it will take quite awhile to get there.