Can't help you with live footage, but maybe with camera placement -
I would place both cameras on same side, but opposite corners. This would help with angles that avoid the ref AND keep the other camera out of the shot. Use shotgun mic for audio since you won't likely be able to suspend a mic above the fighters aka FNF & HBO.
If you can get a couple more cams, try placing one for an overall ring shot (wide) and one on a group of fans for audience reactions.
You might also consider a lav mic on the ref.
Also, fans are accustom to watching boxing with announcers for "color". If you don't have an announcer to mic live, you might consider recording a narrative later.