Fizik sizing

Would like to know the thoughts of any Fizik shoe riders out there.
My Sidi shoes are coming to an end (45), and was looking to move to Fizik R1. I’ve checked out their sizing and I’m in a quandary whether to go for 283.5 (44) or 287 (44.5). My foot length is 280 and debating whether 3.5mm is enough gap.
If it helps I’m a 9.5 in Nike & 10 in Adidas trainers. Cheers