Interesting thread I just found...
You guys mean having one of your girl-friends or your wife (in my case fiancée) crucified alone - or in front of yourself (face to face)?
That's indeed nice: I can highly recommend this sort of play, particularly for those which are sadomasochists like my kinky girl-friends and I (and some of our/their male spouses, which help out as crucifiers next to getting crucified, too).
We use painful saddles (penetrating through the anus + horizontally fixed threaded bars behind these, so buttocks will sit on them safely, but still providing enough pain to make this stunt lingering for us perverts to enjoy). We also apply little tortures (usual SM-stuff like weighted medical clips with teeth on genitals, areolas and nipples, the later restricted in duration though as nipples like some blood circulation from time to time).
Watching your friend crucified while suffering the same way is the coolest SM play we practice in my own opinion (though I like straddling the spanish horse face to face with my fiancée, too). All my female play partners had not been into crux kink, but got excited by the idea when I told them about it and showed photos of my prior crux sessions.
Actually the biggest challenge for our play was to find locations which provide enough room and silence at night - to focus on the actual thing. We managed that thanks to friends with an abandoned former farm house.
No wonder that you fellows do the same treatment to your wifes and play partners...
Some of you may have enjoyed photos of our crux and other sessions on our Fetlife account (since I keep receiving unsolicited "friendship" invitations, however from pretty anonymous Fetlife profiles with no references but crux-kink - so I guess it came from here), and two of you have been crucified with me - sadly the only real contact with a m/f-couple that came through this pretty special kink platform. Would be cool, if people were using it more to just meet and play (what's so difficult about that!!??) - sex, BDSM and good dining together bring much more fun than sitting in front of a computer screen and... clean it up later