Is there a rule that describes how the lips be positioned while reciting idgham meem saakin and ikhfa meem saakin?

Question
assalaamu a'laikum.  Is there a rule that describes how the lips be positioned while reciting idgham meem saakin and ikhfa meem saakin? Is closing the lips to pronounce the idgham meem saakin wrong? I've heard reciters reciting it both closing lips and also by just meeting the lips but leaving some space? For example reading Mimma(idgham). And in tarmeehim bihijaaratim(ikhfa meem saakin), is closing or pressing our lips against each other wrong or allowed? Pls, help. JazakAllah

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh. 
The lips are closed for the idghaam of the meem saakinah into another meem.  There is no difference of opinion on this.  As to the ikhfaa' ash-shafawee and iqlab,  most scholars of tajweed state that the lips should be closed.   There are some who maintain that there should be slight parting of the lips.   His emminence Ash-Sheikh Dr. Ayman Swayd has done over 20 years of research on this subject and came to the conclusion that the old scholars of tajweed and the authentic chains have closing of the lips. 
Please see the following links for more detailed information:

http://www.abouttajweed.com/23070102.htm

http://www.abouttajweed.com/060602.htm

http://www.abouttajweed.com/kb/entry/67/

http://www.abouttajweed.com/the-meem-saakinah/the-meem-saakinah-rules-part-1-ikhfa-shaf.html

http://www.abouttajweed.com/the-noon-saakinah-and-tanween/changing-iqlaab-rule-of-the-noon-saakinah-and-ta.html

For those who can understand Arabic well, the explanation of Ash-Sheikh Dr. Ayman of the lip positioning of the ikhfa' ash-shafawee and iqlaab to a group of female Qur'an teachers in Jeddah has been digitilized by a kind brother, may Allah reward him with al-firdaws, and can be listened to at the following link: http://audio.teamtil.net/tajweed/ayman-swayd/1422_meem/

Wa iyyaaakum.  Wa assalaam