I was in same boat as you a few months ago and went with the Sub-frame build over the Correct Track.
I thought I only need 2 inches but I was way wrong. My fab guy said I needed 6 inches and I am glad I trusted his judgment. I asked him to put extra holes in the new shackles for additional adjust too. It worked out great. Cost me $750 and I was more than happy to pay that after I got a quote for the Correct Track installed at over $1000.
I also upgraded from 15" ST tires to 16" LT tires which gained me another one inch in height.
Here was my thread on upgrading tires and adding the sub frame.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28055166.cfm
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