Redpepper - I need to address this first. I know I wrote a novel and you probably missed it. But please, give us a little credit. We're all educated, intelligent adults.
Prior to our quad R & I have been monogamous for 25+ years, T & S for 15+ years, plus we ALL were thoroughly tested for STIs, plus pregnancy isn't an issue for either couple although just for that off chance both women are using backup. Yes, we had the responsible discussion with them.
Of course pulling out isn't safe sex!!!! That was simply a request that I had made to him because I was uncomfortable with the idea. He pulls out with me because he LIKES to. That's the only reason. For now I had asked that he do so with S as well. That's all.