Hi Erick.
Thanks for your time and explanations.
I do use Yoast and would have loved to see that release that solve the Yoast sitemap issue. But, my membership is canceled. I moved to Envira Pro Gallery.
If support team on NextGEN would have spent even half of the time that you did on the above reply, I would have probably stayed with nextGEN and not write that review.
Your plugin is great but,
1. You can not have a good plugin without a good caring support behind it.
2. Images exposure on search engine is very important if you wish to get traffic to your website.
The gallery images indexed shown on the link that you sent me above are newly indexed. Probably as a result of using a different plugin.