Track width is indeed narrower in the rear of an XC by 60mm, 30mm for an R or V70AWD.
What I do when I "string" a car is remove the hub cap and measure from the head of the axle bolt. The assumption here is that when torqued properly the surface of the head of the axle bolt is equal distant within a few thousands from the car's centerline as the one on the opposite side and that the subframe on that end of the car hasn't been whacked out of position. So I then adjust the string so that the distance from the string to the bolt head is 30mm less (half of 60, right) than the similar measurement at the front. You need to consider this as otherwise you get a toe-out at the front and the thrust angle is screwed up. You then take your toe measurements from the front and rear of the wheels on a plane level with the center hub. When you "string" a car you may not be as accurate as a laser alignment setup, but if you take care especially with your measurements from the references points, like the bolt heads I referred to, and the string you can get well within the spec tolerance. I would also argue that seeing how some of the techs running the laser machines these days do it, I would bet my geezer eyeballs and my string against them any day. When I raced, this is how we setup the cars (Spec Racer Ford, Formula Ford and Showroom Stock cars) and it worked great.
As an example of the level of accuracy you get with a "professional" alignment these days. I just bought a 7 Series BMW that had just had an alignment after a toe link change. The paperwork included the alignment results and the tech had setup the front toe, albeit in spec, unevenly side-to-side and toward the extreme toe-out side of the spec. With the 20in rubber on the car, the car was a bit squirrelly. I "strung" the car, dialed the front toe back about half a turn on the tie rod that was the furthest from ideal and the handling came right back (I did this to make certain I didn't have some kind of un-associated suspension problem). I then went ahead and basically re-did the front alignment bringing the toe-out, in this case, more equal side-to-side and closer to the more zero toe side of the spec. Now the car handles rock solid. It is important to remember when you do all of this that things like wide tires, especially those with extreme low profile (this car has 40s in the front 35s in the rear) can really react to slight changes in toe so it doesn't take much to throw the handling off or bring it back. But in any event, there is no reason that anyone with 4 jackstands, a ball of string, a metric rule, a bit of level pavement and an hour of time can't do an alignment, at least for toe. Camber is a bit more of a pain and it is helpful to have something like this (http://www.longacreracing.com/produc...%84%a2-Adapter) to do the readings. I actually made my own using some 3/4" angle aluminum and a digital level and it works well enough to get within a couple tenths of a degree. And for me the real advantage is that I can correct an alignment issue (thanks for our crap roads here) straight away and not suffer any undo tire wear as a result.
Anyway, my two cents
Cheers,
Bill
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