How is the wing incidence of a semisymetrical wing usually set in relation to the horzontal stab?

If I draw a line through the wing from the middle of the leading edge to the middle of the trailing edge (meaning that there would be more wing above the line than below the line) and have this line be parallel with the horizontal stab and a couple degrees of engine down thrust, would this be a good starting point that would result in a decent flying R/C plane?

WRK

That would give you a 0-0 wing to stab difference. Maybe not a good thing. It would trim in the end but it would do so with some up elevator trim. And many consider permanent trim on a surface to be unsightly. You'd be better off to set the stabilizer about 1.5 to 2 degrees negative to the airfoil centerline that you described. Which, incedentally is how we all describe the airfoil center line and if very proper.

If it'a a sport model then 1.5 to 2'ish would be enough since you'll likely put the CG back far enough to make it balance out the trim. If it's more of a trainer with a higher degree of pitch stability then 2.5 to 3 difference would be a good starting point.

The closer to 0-0 you set all this the less downthrust you'll need. As it gets more into the trainer realm you'll find you need more downthrust to avoid a strong nose up reaction to changes in speed related to throttle use. With a 3 degree incidence angle difference in the wing and stab it would not be unusual to use 4 or 5 degree of downthrust angle in relation to that wing center line.