Would the Directory Of Ezines work for blogs on one specific weight loss product?

Hi, I've read every post searching for 'directory of ezines' in the title, and read their sales thread.

a recurring theme was that people get poor results because they aren't choosing correctly targeted sites to contact for article syndication and solo ads, or their ad isn't compellingly enough written.

I have 8 sites all on one particular weight loss product. The problem is that nearly all the content is about that one product, I try to be informative and write interesting content, but I'm concerned that if I try to get into article syndication, and I join the Directory of Ezines, my content won't be broad enough to get good results with article syndication.

The other main way to be successful using the DOE appears to to through solo ads. Here I'm more concerned to find out if anyone in the weight loss niche has tried to sell a particular weight loss product through these ads. Were you successful?

While I can see many advantages to article syndication, the one fundamental problem for me is that even if I get my articles posted on sites in the same niche, and I get my ezine article ads in front of readers in the right niche, that still isn't nearly as targeted as someone searching "product name reviews" in Google.

Perhaps one way around this would be to try and target the subniche for the product. So this is a weight loss product, in this case it's a diet pill. Do you think DOE is large enough to provide sites on many diet pills? That's surely as targeted as I can get?

Thanks for any advice!