I'll add some info, too, since I use the MDC archives to find info so often!
We saw several of the Louisville professionals mentioned above, and all of them missed my DS's posterior submucousal tongue-tie. I ended up e-mailing several experts (members of the International Association of TT of Professionals) from around the country to find someone closer to Louisville. The closest person I could find was Dr. Greg Notestine, a dentist in Dayton, OH. I contacted him via e-mail, and he was super nice. He told me what photos to take of DS's mouth, and I e-mailed those to him. He identified restrictions via the photos, and we went up the first time 3 weeks ago to have my son's tongue and lip released (I didn't even know about lip ties at first!). We went back yesterday for my son to have his tongue released a second time. Dr. Notestine's website is http://www.smiles4udayton.com/, but the website does not mention TT. He's clipped over 3,000 babies, and has written journal articles on the subject. I was so impressed with his knowledge of how a baby's suck functions. My son's issues with gas and spitting up made so much sense after talking to Dr. Notestine!
From what I've read, the posterior tongue-ties can be very difficult to diagnose, so I encourage all mama's out there to follow your gut instincts and keep searching for answers. I had given up on the idea of TT thinking I was wrong after seeing several location LCs and an oral surgeon. It ended up taking me 5 months to figure it out, and I wish I had gotten a diagnosis sooner.
Here is an article that really helped me:
(The LC who runs that site will also consult with you via e-mail... she's based in the UK, but she is SO helpful!)
This site also helped me figure out my son had a lip tie after reading this mama's blog post:
This site has good info on other implications of tongue-tie beyond bf-ing difficulties (this site has made me seriously consider that I may have a posterior TT that was never diagnosed/treated):
And of course the MDC archives are a fantastic resource, but it takes a lot of time to sift through the old threads and pull out info!