>What would be the best technique to use to add two new items on top of an ArrayList when I have some items already in it and I would need those items to drop down by two positions each?

I would think: ArrayList.Insert()

This example show how to add 2 items at once:

http://msdn2.microsoft.com/en-us/library/system.collections.arraylist.insert(VS.71).aspx

(You'll have to cut and paste the URL, the autolink is skipping the .aspx)