Even if you aren't into a specific kind (or kinds) of women, it's generally a good idea to emphasize what you DO like rather than what you don't like. In your case, we can all respect that you may have a taste for petite or athletic white girls or tiny Asian or Latina women. It'd go over fine if you put it that way. When you phrase it in an exclusionary manner, you run the risk of people jumping to conclusions about your underlying motivations. Even if they are your target market, there are going to be some slender white women who don't want to give you the time of day because they don't like racists (and maybe you're not racist) or people who discriminate on size (and maybe you have a lovely BBW sista as your wife that you adore and your hobbying preference is for variety).  
   
 Me personally, if a woman's listing says "no black guys" that's a non-starter for me. Not because I'm black, but because I don't like bigots. In some cases, there's a perfectly fine motivation for not wanting black guys (ie her black husband is fine with her fucking others, but wants his to be the only bbc she rides) but the way something is communicated just rubs me the wrong way... And I'm in this hobby to be rubbed many ways - except the wrong way.  
   
 Best of luck!