I say go for it!
Yeah i guess you could lose some of your exclusivity but you never know by working on more sites will bring more people to your own site too.
You've definitely picked some really good websites to work for.
I love Kink.com not really for all the BDSM but for how professional they are. They really do seem to look after there models.
I'm a member of TheUpperfloor and two of my fav models working on there are Krysta Kaos and Skin Diamond! Two models who unfortunately for me i would never see on FTV because both models have a lot of tattoos. I think i was one of the few guys on the old FTV forum who likes tattoos haha!
So yeah i would love to see you on sexandsubmission, thetrainingofo, theupperfloor, everythingbutt take your pick and i'll download it!
X-art is also another very good site.
If you ever worked in europe Vivthomas.com is a very good website too.
evilangel.com is one of my favs as well.