Confession: the trickiest part of an installation is almost always mounting the mobile to the ceiling. There are tons of types of ceilings, and since we don't usually visit the installation site beforehand, it's The Big Unknown.
We discovered this at our very first installation. We were installing several pieces at a rec center with a ceiling coated with an acoustic drywall, and we had no idea where the support beams were. Let's just say we learned more than a few important lessons that day. (Er, three days...)
The piece we created for the Rockingham Hospital last year had more than 50 mounting points. For each one, we had to remove the tiles from the drop ceiling, find a secure mounting point, and string the cable through the drop-ceiling tile. Matt spent a lot of time in that crawlspace. (See below.)
And at our last installation, the drop ceiling didn't have removable tiles, so Matt actually had to crawl through a three-foot crawlspace while staying on support beams to secure the sculpture's mounting point. Despite his grace, Matt decided he better not change careers to cat burglary.