I think if the pin breaks the whole bungee retainer comes off from one side and you can lose your Gear anyways. The only added safety is when a single bungee strap breaks the other one holds it in place.
It depends on the setup of the bungee retainer. I've seen some that are completely independent where the only connection to both sides is the bungee. In these setups, you are correct. A broken pin is a single point of failure. Other designs are a single piece. In which case, a single pin breaking will not result in an unattached computer.
Question - I have relatively thin wrists and that leaves a lot of extra strap length I need to tuck in somewhere. If using a bungee can I comfortably mount my DC higher up the arm closer to the elbow without it slipping and sliding down to the narrow part of the wrist?
You should be able to. Thinner bungee is easier to stretch, so should probably work better.
How comfortable is a bungee when diving with shorty on a bare skin?
I never dive with completely bare arms, but frequently dive with a rash guard. My bungee mounted Perdix is quite comfortable. I usually leave it on during the surface interval, even if we move the boat to a different spot.
If it's too tight, it will not be comfortable, no matter what. So, I'd suggest starting with the bungee a little longer than needed, and you can adjust tighter if needed. Also, if you regularly use varying exposure protection, it might be worth it leaving the tails a bit longer so you can re-tie for the thicker wetsuit/drysuit times.
Oh, and BTW. I nearly lost a computer due to a broken strap. Luckily it happened at the perfect spot. Was diving with my daughter on her checkout dives. Fell from my wrist while we were on the entry platform (normally dry) but heavy rains had it underwater. Carried it for that dive, then ordered a bungee mount immediately after.
