Where in that cage does he hang out and fall?

Yes, definitely make it a "no-fall" zone. I've had chondros wedge themselves in the lip of the Vision 222's, and fall. Thankfully I have not had them injure themselves (and thats counter-intuitive to the recommendation), but I've SEEN them fall. It's a long drop, and unlike cats, they very rarely end up landing on their feet.

Yes, the "lip" over the glass. That's where he falls from usually.  Sometimes he'll flop off a suspended limb, a much shorter drop, and yes, he usually lands twisted or on his back, and I worry if he were to fall on the lip of the water bowl or edge of the rock hide. 

While it did not happen in my care, I have a ball python with scarring and deformity from a fall. I had my carpets in a tall cage with limbs to climb and my male would occasionally fall and catch one of the other limbs or the dish. I did not see any swelling or feel anything out of place but then he was only dropping a foot to 18" at the most.  I have seen a few blurbs in books and online articles about broken backs from falling. 

considering that i cannot even see the snake in that enclosure (of course, if it is even there), i see those perches are way too thick.  a perch that thick would be better suited for like one of my adult boas (6-7-8').

i recommend replacing them with thinner perches, and more of them.  maybe a few in between the high areas and the ground level to help break a fall.

worst comes to, i'd straight remove the more dangerous perches (the higher ones).

like it has already been mentioned, snakes can bust themselves up with a good fall.

i usually see no need to provide elevation for semi-arboreals, they do not need it and thrive well without it.

They may not "need" it, but that gets into the whole enrichment thing, which I think our cages generally are too sterile for "exploring".

It may be more for me, but I like the more lush cage setup. It looks fine and all that, but I think a complex environment is closer to nature and more beneficial than just four walls.

Well said.  I've noticed the snakes become more active (exploring with tongue and movement) when I make changes and not taking advantage of vertical space is terrifically inefficient.  Some years ago our herp society took a field trip to one of the two big zoos here in Chicago and learned from the keeper at the reptile house that "enrichment" was being used for all the reptiles including snakes.  Some scoffed, I thought, "I'll try it."  Glad I did, it clearly increases movement/activity, and that can't be bad.

Anyway, thanks to you all for answering re: information about fall injuries in snakes.  I'm going to add a couple branches extending from the lip over the glass to the large branches up against the wall, hang some fake plants over it, the whole setup is not using space well now, and I have to protect this guy from falls.  On one hand I figured, "oh this must happen in nature all the time" and on the other hand, "I wonder if they can break their bones!"