OK, looking at the coverage I have no coverage extending more than 200nm west, north-west or south-west on the Radarbox screen. And this includes a significant gap over New Plymouth, however, all flights from Auckland to Christchurch 90% of the time fly overhead the NP VOR and all the Auckland to Queenstown flights fly further to the west than New Plymouth but the coverage is not showing for these flights. Attached are some database captures of my ADS-B coverage for some of the flights from Auckland to/from Melbourne where the range is greater than 200nm. Similarly for Wellington to/from Brisbane (QFA355/356) and Wellington to/from Sydney (ANZ240/249).Also screenshots showing ANZ273 and QFA356 on standard routings in the clear coverage areas.
So I'll say it again, the coverage appears to be some 50nm off centre to the east, I do not get flights that far east, only UAL use that sector plus the very odd private jet heading to Christchurch but much further west than the coverage outline would suggest.
I would appreciate some 'developer' to check the centre co-ordinates for the coverage outline as they are not the same as my receiver location.