Hello, I am kinda coming back from the dead here after a long hiatus from this site, but not the poly lifestyle.
I am married. I am very much poly, my wife is supportive of me, but not really looking for anything past friends. I totally feel your pain.
I am currently off OKC, but when I was there I was always upfront about my situation within the first messages exchanged. I can't be ok with leading anyone on. I love women, and feel like a good portion of the male population treats them poorly anyway, so I refuse to jump on that wagon. I am not only enabling a gender stereotype, but also possibly turning some poor girls first exposure to poly into something that leaves a really bad taste in her mouth.
OKC is the ONLY place I have had any luck with anything. I have dated both openly poly women and women that were not poly, but though enough of me to date and explore accepting it.
I have sent out about 4 bajillion messages. I have got a handful back. Few mean words, mostly no thank yous or chatter than burns out fast.
I can't remember how I worded my profile. I listed as "available" (And don't assume that tells the story, people don't notice there is "single" AND "available"), mentioned I was looking for new connections and open to seeing where things go, and in the "most private thing I am willing to admit" box, wrote that I have a deep interest in poly and open relationships. its a good primer. If people find the concept icky, they can stop right there, and if that doesn't phase or intrigues them, we can chat and expand on the topic.
Blatantly putting out there that your married is blunt honesty, but will likely deep six any chatter before it begins. Its more likely someone will consider accepting you if you have had the opportunity to catch their attention via a few well written messages first.
I am ALWAYS open to friends when they decline, and have a handful of friends to show for that.