Caravan can also bend the firewall if you take it in to water that is too rough due to the long nose. However they'll take quite a bit.
Now it should be noted the Beaver is far from indestructible.
Rocket, what will be your areas of operation and have you considered the "other" Cessnas?
I know Strahan used to run Maules as well (maybe they still do?), haven't had any dealings with Maules but that may also be another avenue to investigate.