There letter Ⲏ is pronounced "ee" in GB (Greek Bohairic)
and it is pronounced "ee" Or ā in the original pronunciation
The church adopted the GB since about 200 years ago
And it is the one that is used in prayers, and Dr.Kamal Farid is one of its teachers
but this is not the original pronounciaton that was actually used by copts when it was a spoken language
Have you read this article?
http://kame.danacbe.com/index.php?topic=2.0I can provide many proves for my claim, but i don't know which kind do you want
1- there is manuscripts (coptic text with its pronunciation in Arabic)
2- the current pronunciation of names of famous copts who lived in the past
3- current pronunciation of Names of some cities in Egypt
and if you want books then there is
Coptic Sounds By W. Worrell
http://links.jstor.org/sici?sici=0097-8507(193406)10%3A2%3C220%3ACSPITM%3E2.0.CO%3B2-QCrum Dictionary: (it is very famous and well known)
Book of Fr. Shenouda Maher
tell me if you need more