i want to a ask a question regarding qaedat aqwa as sababeen.

Assalamu alaikum

i want to a ask a question regarding qaedat aqwa as sababeen.
i know that there are varies degrees in mudood, and two mudood rule in one word (2 cause for a legthening) and use the stronger one. my concern is in surah fatiha second last verse 'waladdoolin' it has a madd asli (dwad with fatha followed by alif) and its also merge madd leen. would you consider it to be aqwa sababeen, although madd asli tabi is not mention in the varies degrees of mudood.

may Allah bless you

Wa alaikum assalaam wa rahmatullahi wa barakatuh,
The definition of the natural medd, (aSli) is that it is a medd letter NOT followed by a hamzah or a sukoon.  Whenever there is a hamzah or a sukoon after a medd letter it is no longer a natural medd, but instead becomes one of the secondary mudood (). 
In the case of the word , there is a medd letter (the alif) followed by a laam with a shaddah.  The shaddad means two of the letter, the first of it having a sukoon, so this makes it a secondary medd. 
This particular medd is called and is lengthened six vowel counts.  To read more about this medd please see: http://www.abouttajweed.com/the-mudood-the-lengthenings-/the-mudood-lengthenings-part-8.html
This six vowel count medd is followed by a another medd letter (the ya'), not a leen letter, and when we stop on it, then the last letter acquires a sukoon, so again this s a secondary medd.  This specific medd is called .  To read more about this type of medd please see: http://www.abouttajweed.com/the-mudood-the-lengthenings-/the-mudood-lengthenings-part-7.html

There is no sababayn in this example. 
Wa iyyaaakum.
May Allah bless you also.