I have used (and still do) the 60 X 120 set up. I shoot only vanes, and love rthe setup. It also gives better fletch clearance than the 90 x 90. I use 4 - 3.75" vanes. This comes out to 15", the same as if you used 3- 5". THe vanes give a lower provile that the 5" also. I fletch them in a hard left hand helical, and use a florescent "hot pink" color. Very easy to see in flight, and find if you miss.
I have used this configuration since the late 60's when I was shooting NFAA tournaments. Of cours back then it was shorter fletch and with feathers.