Yeah I did consider a double dry hop, and If I was able to crack open my fermenter lid, I probably would, but I can't risk the chance of infection on this one.
Stuffing around with kegs and pushing from one to another.
I think the difference also is this:
A lot of people dry hop into a 18c-22c beer. Correct me if i'm wrong, but in my mind, at that temp you'll also be extracting harsh acids as well as the resins you're after. Dry hopping in a beer that's 2c-4c will not extract these harsh acids as much and leaves the alcohol to extract the resins you're after and less of the harsh acids.
So I think maybe 500g for 7 days and then if it's still not there, another 250g for 5 (making it 1.75kg, I have more Amarillo

)
With a brew @ nearly 10% ABV I dont think there will be any problem dry hopping 500g
Cheers,
BF