I think I'll buy some stock in TopFlite. You're using way too much covering in your method. As previously mentioned, all you have to do is tack the corners and ends, seal all the way around and then shrink. I almost never use a heat gun. I use an iron. If you get it too hot you'll melt through it or apply too much heat that when it sags later on you won't be able to re-shrink it.
One thing you have to remember is that although it is not visible, there is a grain in Monokote and it runs the length of the roll. You want this grain to run spanwise on your wing and tail surfaces otherwise as you shrink the covering it will not bridge the ribs and will cause a droop between them.
Here is a video of Solartex being applied. Same prodedure as Monokote.
http://www.youtube.com/watch?v=ChviyGPH_lI
Bob