Yea while eye protection is important no matter what laser you are using these laser systems are huge so it's not like a hand held thats going to roll off a table and flash you in the eye. Also you are right there are some adjustments that you need to see the beam to make. If It were me though I would still be kind of worried about the possibility of one of the optics somehow failing and then you will have NO CLUE where the beam is going to end up especially while making adjustments. I'm sure there are a lot of precautions taken before letting anyone work on the laser(s) without eye protection.
50cm aperture.... wow. It makes sense though, you'd need such a huge aperture for any kind of useable divergence.
I have a somewhat related question though; what is the name of, and cause of; the phenomena which causes the beam to suddenly dissapear abruptly from sight at some distance? What determines the distance? I know those photons don't just suddenly say "we're stopping here, sorry!". Why does the beam not appear to fade out gradually?
Ever look through binoculars at a beam...it's interesting. I was able to hit a cloud by using a telescope as a beam expander with a green laser when it was snowing a bit. I saw it even without the binoculars....but I confirmed it with them. I think for non expanded beams it could be a combination of divergence and the air getting thinner as well as the angle relative to the eye...which could mean past a certain point the brighter beam blocks the thinner and much dimmer beam out.