The Path to SL155: Where to for jolly cooperation?

Hello everybody. I'm gunning towards SL155 (roleplaying build); right now I'm at SL110, NG+. Did a 2 hour marathon tonight; defeated Quelaag, the Golem, O&S and the Four Kings. Is there any place where I people tend to coop a lot at my level? I don't think the remaining bosses will give me enough souls to achieve my desired level.

Just in case that's not an option, I went with the Darkwraith Covenant.

Im pretty sure there are always people looking for help for the 4 kings on NG+.

Where would be the best place to put the WSS? I went into the New Londo Ruins as a human and couldn't find a single sign. Killed them two hours ago. And there was I thinking that my Lightning Uchi +5 would be obsolete by now.

I've found people still doing O&S at high SL's, though every now and then you'll get summoned to a dark anor londo to gank. I usually stand by and then watch as the invaders kill the host, but if you are interested in just Co-Op I'd just black crystal out and move your sign a bit.

I think on the platform after the first bridge is where you put it.

Archives as well

O&S is one of the best areas for jolly cooperation. Four Kings is all right but is not always full of people needing help.