I have a question in regard to stopping on a word that have alif tanween just like in Surah Al Kahf for instance.

Question

Assalamu aleikum dear Staff members,
May Allah bless you all in this blessed month of Ramadan and may He increase your scale of good deeds for the terrific work you are providing the Muslim community thanks to your site.

I have a question in regard to stopping on a word that have alif tanween just like in Surah Al Kahf for instance. I previously read on your site that stopping on such word such as in ayat 1 surah Al Kahf: "'iwadjaa" is done with 2 counts. However I have noticed a few imams (in my city) lengthening such words a little longer whenever they end their recitation in salah; which sounds, to my ears, as if they lengthening the word 3 or even 4 counts. My question is:
1. What is the correct medd used when stopping on an alif tanween word?
2. Is this a tajweed mistake to lengthen such a word even to 3 medd?

May Allah protect you and help you find the answer to those questions.
wa salaamu aleikum

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
We apologize for the delay in answering your question.  We ask Allah accept  all our fasting and righteous deeds and grant us all a blessed Eid.
1.  The correct length for stopping on a word ending with a tanween fath is two vowel counts.  It is which follows the natural medd.  There are a few exceptions.  Please see: http://www.abouttajweed.com/the-mudood-the-lengthenings-/the-mudood-lengthenings-part-2.html for full explanation.
2.  It is not correct to lengthen it more than two vowel counts. 

May Allah protect you also and increase you in beneficial knowledge. 
Wa assalam alaikum wa rahmatullah.