Been doing this awhile.
Our free speech attorney has told us, that yes. . .penetration WITH bondage is considered rape. So we don't depict it. And incidentally, flogging or spanking someone tied up is a depiction of "torture", so we don't depict that either.
Another thing to consider- There have been over 20 years of studies by sex therapists on "Positive Outcome Rape" This is where it starts without consent then the girl (usually) decides she LOVES getting screwed by the guy and it changes to "oh yeah pound me harder". On the surface this seems ok, but what all the studies have shown is interesting. What they do is divide a large group of normal people into two groups. They show 50% a positive outcome (or fantasy) rape scene then a real violent rape scene. The other group they show regular consensual sex then a real violent rape scene. In every study since the late 70s, the results were the same. The two groups of people saw the real rape differently. The people who had seen the fantasy rape scene rated the violent rape scene as "not as bad" as the people who hadnt been exposed to the fantasy rape scene. As a result of all this research I dont promote anything that is not consensual - even the obviously fantasy stuff.