We lived by the 1st rule of this lifestyle 'preserve the primary relationship. That relationship was her & me, NOT her and one of her partners. I will admit that when we first started she was like a kid in a candy store and it a took a bit of time till she/we got her/our 'sea legs'
Cage was never even a part of any discussion. We discussed and agreed to things that worked for us, yes, sometimes the things fell through the cracks. But the one that was never broken was she was in charge, When it came to her partners (bulls) she/we lived by the master rule 'she who has the pussy is in charge'. If she said NO it was NO!
It was my choice to be present or not, call it the right of 1st refusal. At times I'd join in when she wanted or/and allowed me to. Mostly I'd watch and stroke. I'd never cum before they were done. Sometimes I'd actually nod off into nap land.
I don't think there is a more sexual high than watching your woman have sex with another man. And as enjoyable as it was for me her pleasure was the reason, think compersion.