Center the wheel within the swing-arm and measure from a common point of reference on the swing-arm to a common point of reference on/or center of the rim is how I also do it.

Swinging around an 8' flourescent tube sounds more dangerous to me than riding with the wheels slightly out....but, I also have seen budget builds where centering in the swing-arm doesn't work esp. old weld-on rigids that were 'heat and beat' to fit. So, that is why I support alignment front to rear sight unseen.

 

I've always just measured the distance from the swingarm pivot to the rear wheel axle on each side with a tape measure. Assuming your frame and/or swingarm aren't bent or otherwise out of whack, that should work.

 

I have another (long term) build project of a softail, the manufacturer recomended that after centering the front wheel on the springer front end, and center the rear wheel on the frame swing arm, i should check alignment of both front and back to be sure that the front spacers are right and everything is indeed aligned. it was my understanding that it was to be done once.

I apologize for my mistake of stating (alignment) when i should have stated (centering) on the post. Thanks for the valuable info on how to do both, for me at thispoint knowing all the ways is priceless.

 

The problem i find with this is that the swingarm pivot on the left side is not accessible because it is behind the case, so is difficult to get an accurate measurement.

 

I guess it's different on various years of Sportsters...mine is easy to get to, easier than the right side.

 

I just project a Holographic image of both wheels super imposed, one over the other, on the back of the shop wall.
Then sit in the saddle and blow the horn, while looking for axial deviations in the line up. (Hic-cup!) Where is the fridge?
pg