My cars number plate is centre mounted on the jig welded chassis. Even if it wasn't, as long as the target masking tape graduations are centrally positioned with the chassis, it will be OK. The number plate is just somewhere to stick the target, the back of the plate is in a good position.
As someone mentioned, check the rear wheel is mounted in the centre, some appear not to be on some early cars. If you use the laser level against both sides of the rear tyre and the laser dot hits the target equal distances from the centre you have aligned the rear wheel along the full length of the car, without the need to keep checking triangulation measurements, easy. Check the rear wheel is still aligned after tightening the axle nut fully, it tends to move.
Looking at moving machines is fine but working on them is a risk you decide on. I still have all my fingers after 40+ years in engineering.
