Weft/Extendtube questions!

Hello, I'm a bit of a newbie but I've been reading A LOT of posts and into about the various extension methods over the past couple of months.

I've decided to do a weft install using extendtubes on my hair, but I'll be doing it myself so I have a few questions first!

1)I've experimented with clip-ins in the past, and noticed that they seem to have 2 or more layers of weft sewn together.. When installing wefts with glue or extendtubes, do you just use single wefts and do more rows?  Or do you still need to double them up first?  (I hope that made sense)

2)Is there a way to put wefts in the hair using extentubes other than this method - http://www.drlocks.net/linkiestrack/index.htm ?  For example, would it work to just take a piece of hair from above the weft, and a piece from below it, and lock them together?

Any help would be hugely appreciated.  Thankyou ladies :)

When I do my wefts, I like to get a lot of hair on 4 tracks, so I think I double or triple each row.