Dave's quick rear wheel check is some of what i was suggesting in my first post to this thread. My method of two straight edges along side of both rims would involve the fork/ft wheel with the rear. Not sure where one would get two , almost, 6 foot straight edges that could be sandwiching the rims... maybe 8020. Also both methods dosen't really consider the wheels' vertical alignment (not that the vertical controls the bike''s tracking much).

Dave- If I understand your method, it won't take into account the BB shell being offset. Might making two marks on the tape, from each side of the rim, then flip the rim and remark both sides of the rim be a better indicator of the wheel's alignment WRT the bike's centerline? If the wheel was well centered then the marks from the drive side of the straight edge, one each with the wheel installed both ways, be on top of each other. As the lines fron the nondrive side of the straight edge would also be on top of each other. In other words you'd have two pairs of lines and if the frame was not aligned well the two pairs of lines would be a little bit off set from each other. Andy.