sraggered wheels and alignment

I just upgraded to 18 inch rims that are 9 inches wide on the front and 10 inches wide on the rear. I will be using SO-3's on these rims. Should I get my 97 Cobra aligned before putting these wheels on or after? I was told by a local alignment shop that it is impossible to align the car with staggered wheels. Anyone know anything about this? It made me wonder how they align duallies and other cars with wider rears. I posted this on other forums so I appologise if you have seen it before.
Aaron

I would have the car aligned with the new wheels/tires. If you go with a wider width tire they will have to be exact with the alignment settings since the setup will be much more responsive. There is no reason they could not align the car with a staggered wheel setup (unless they don't have an up-to-date alignment machine.

Thanks Grant.
That makes sense to me to. I will take my business elsewhere. I guess I will try Sears they usually are up to date. I will also take your suggestion and go ahead and mount thetires and wheels first.
Aaron