Agree. Sure, the underwriters will ask for more information, but not guarantee you can buy it.
It is much better to buy through the associaction as I worked for this matter before. Third party
only ---- HKD3M or HKD5M public liability - normally the premium is about several hunderd to thousand.
I don't know if Hong Kong companies offer insurances for this.
However, in foreign countries, a lot of companies offer these insurances, and under these insurances, the companies will pay compensation to the victim as long as RC helicopters accidents happen in designated areas.