Heather has given you some sound advice.

I have joined couples both M-F and F-F and have had good experiences. There has also been a less than positive experience. Now I am in a couple and that could be a good thing from the other side. If that were to happen avoiding pressure both for the third and us would be important to me. Everyone needs to be comfortable and feel good about it.

My interests today also include the possibility of a relationship with a woman that respects my present relationship. While sharing with both would be nice, some feminine time is a good idea to me as well. In this I do not exclude an intimate relationship that does not include sexuality with my male partner. Yet, even in an exclusively femine arrangement I would want that woman to be open to my present partner as a friend and not just that attachment at home. I would want both to be aware of and have respect for each other.