High Value Loads, how often? Cargo Insurance set up?

I'm in the process of getting everything set up as an O/O. The standard cargo insurance amount seems to be $100k for all of the insurance carriers. How often do you folks get loads that are worth much more? My business will be hauling a lot of wine, and I can see loads frequently being worth much more than $100k. Should I just go for a higher limit in the beginning, or buy the $100k limit and get riders on the policy to increase only as needed? How are these issues spelled out in the rate con?

 

The insurance companies already charge a premium for wine hauling because shippers tend to inflate the value of the wine. But I'll just need to get a flat $500k to be safe.