hi AshEB1,
Regarding my credentials. Since i just graduated with my PhD there was nothing really very strong. One thing that i did was to link all my research to Environmental pollution, that is when i did my cover letter. The cover letter is real simple like a story. i knew nobody in the immigration office would be able to follow complicated things, for this reason, i made it real simple. only you know your research for this reason, i did not hire an attorney. I knew, down the road if i had gotten a RFE there is nothing much that a attorney could do.
i emailed the department of environmental pollution and water safety people in the state and asked them if they could give me a letter of recommendation based on my thesis. They had asked me to come to their office and give a small presentation, which i did. after that they were more than willing to give me a letter of recommendation. That letter had a state letterhead. Thats about it. Regarding thickness of the packet. mine was around 2 inches thick. i collected a lot of brochures from the state regarding environmental pollution and water quality statistics and made my packet thick. that is all i could really do, especially since i do not have many publications.
I think, if you organize your packet properly, you should be able to do it.
All the best.
Thanks