I'm not sure how viable these sites actually are. There was a huge influx of sites and members in the 00's and some became commercial ventures. However, as most people subsequently find, the sites are full of day dreamers, fantasists, fake profiles and time wasters. Added to that is the issue of work/reward.
Swingingheaven used to be the site about 5-10 years ago. Then it was bought up, they charged for certain services, which pretty much killed it dead. The chances of a single bloke meeting anyone on there (or anywhere else) is slim to none