I put my front wheel a little to the left of center. Usually running the left read in the cage ruts unless it's been raining. After hydroplaning twice and having to have the seat material removed from my posterior crevice I moved far to the right getting both rear tires out of the ruts and the accumulated rain water.
As far as trucks passing me. Living in West Texas, cattle country, we transport a lot of your prime cuts of beef on 4 legs down our 2 lane and 4 lane highways. AND surprisingly this transportation puts a lot of stress on the bovine causing a liquefaction of their previous days meals. You should take extra care when passing the trucks or being passed by these trucks making sure you get to the furthest opposite side of the road or you'll end up in the wash bay of a truck stop. Have on occasion pulled in, raised my arms and said "hit me"......once the laughter subsided they did a dang good job getting all the green bovine exhaust fluids off me and my bike.
8~\o