I used 3/4 of a super ripe navel orange for my first mead (1 gal), and it's still going at day 77. I just cut up slices, peel and all, squeezed them a bit and tossed em. In the beginning of the ferment it was like drinking orange furniture polish, waaay too strong. By now the flavor is waaaay in the back, barely there at all. If you decide to add the orange more towards the end of the ferment, instead of the beginning, I assume the flavor would be more up front. And you're already using orange blossom honey, so I don't think you'd need much. Maybe rack on to some oranges in your secondary.