I know this is quite old but i figured i'd reply. So, I'm always anxious and nervous whenever i publish a request for those to see. It's always pretty nerve wrecking, but i guess the best thing you can do is literally push yourself to do it, but be firm on your stances especially if you want the plot to be the main focus, sexual fetish being secondary. I heard forums like Black Dahlia have a much more broader audience who are much more accepting when it comes to sexual fetishes in general if you are interested in checking it out, but i have yet to use it. In my experience, I have my Rp requests get ignored for long periods of time, but eventually it gets picked up by a few.
The best thing you could do is write your request and make it clear you want plot mainly, and just keep looking. You may even have to wait, but i'm sure someone out there will be interested in your idea.