The top of the hive is the most important place to have insulation. It's the warmest, so the most heat would tend to be lost there. And, more importantly, a cold top will lead to dripping condensation and wet bees. This is an easy solution to that. A piece of styrofoam would also work, and is cheaper, but this is easier and has some other minor benefits.
These tops are indestructible, latch down tight to prevent robbing, and won't blow off in the end. You don't even need to put a rock on top.
I'm not going to claim that a fully latched down Apimaye hive is completely bear proof, but I think between the difficulty of entry and the stinging insects inside, most bears will be deterred. They might push the hive over but would likely not gain entry, unless maybe if they were very desperate to feed.