Take a long straight edge, lay it on floor next to the track snug up against as many lugs as you can with enough of the straight edge going up to tip of ski. Mark center of ski front and back, measure from edge of straight edge to centerlines front and back, use another level (or plumb bob) at front ski tip to bring your centerline down to tape level. Your distances from ski centerline to track should be pretty close to to the same for each side unless something is bent. Set your desired toe out.
P.S. make sure your track is aligned true first (same amount of track sticking out past rear bogey wheel on each side)