In re: five gallon plastic paint buckets as bearproof caches.

All a bear would have to do to pop one open would be to sit on it, or bounce on it hard with its forepaws and its weight behind them. Your only hope would be to odorproof one and bury it, or else just trust to luck.

Depending on the level of bear activity and how human-tolerant the bears are, trusting to luck could be either a fairly good strategy or a hopeless one.