Question about picking a setting

[Rachel37134]

Hi, I am getting a great deal on a great diamond- 5.5mm x 5 cushion cut e color si1. I am looking for settings and having trouble since it's a tiny bit off regular dimensions. Therefore I need some help! Do you think I could put this diamond in a 5.5mm square halo? Or would I be better off with a 5mm or 6mm cushion halo. Any advice is greatly appreciated. I am talking to a family friend jeweler tomorrow, but don't want to sound stupid or insult his profession by my lack of knowledge. Thank you!