I have 3 main sites.
These sites use around 900 keyword combinations.
I have developed a private blog network that's 3 levels deep including the main sites.
The sites have moved into the top 30 on most, with many lesser used keywords on page 1.
I need to send these to page 1.
Should I backlink the third level that uses aged, high authority domains from another network to give me the push?
I'm willing to sacrifice that level and will rebuild 3rd level if needed if discovered.
I do not want to loose the inner 2 levels.