I found your post, 3 years late.And am wondering, did you ever get a response, or find out any information on Rachel Allen, and/or James Allen?
I am descended through Matthew Thompson and his second wife Rachel Allen.
According to LD McPherson's research in "Hamiton, Baskin ad Related Families":
Rachel was born in Augusta county Va on 09/20/1762 according to the christening records of Old Stone Presbyterian Church, she was the daughter of James and Mary Allen.McPherson also states "that James was a Capt. in the French and Indian Wars".
According to James' will "signed 04/28/1788 and recorded in Augusta County, VA 10/18/1791 naming " daughters Rachel Thompson, Margaret Bell, and son William Bell (?), Agnes Shields, Rebecca McClure, Elizabeth McNair, Mary Allen, sons Frances, son-in-law David McNair, and son James Allen, bequeathing to my son James Allen, my home plantation"
Hope this is not redundant for you-and would like to exchange any information any one might have on James and Rachel.