The option to submit flight reports using hand drawn polygon shapes, rather than circles, is only available for commercial-flight users and commands a further premium on the respective API licence fees. So we’ll not be offering that as a feature I’m afraid 
When submitting a flight report we default to a 500m circle radius simply because that’s what the NATS app does and because it’s their assumed VLOS value.
I see no reason why we couldn’t give you the option to make it a smaller (or bigger) radius though. Is this something other people would use? 
