Chris,
Oh takes cialis 5mg every second day, but not on injection days. As long as he moves about afterwards (I've morning and not evening) there doesn't seem to be any ill effects. On the days we choose to have a furtle around but not use an injection, the cialis seems to help. He does get an erection, but as you say, it's probably not useable. We've not tried, and although I'd like to see if it is useable, I don't want to turn it into a disaster if it isn't.
From our point of view, it REALLY isn't all about the actual act, it can be just as enjoyable without penetration. Not better, not worse, just different.
L x