The straightedge for marking the dovetails should have a smaller angle than the dovetail to horizontal angle. The actual angles mean nothing, you just need to carefully match the plane of the dovetail to the plane of the straightedge so they rub together evenly, then read the results. A straightedge with a 45-50 degree angle is useful for all larger angles. Of course, the angles of the sliding side of the compound need to match each other, the gib side surfaces need to match the gib angles (or vice versa.) Read Connelly some more...