I use the Wheaton on my TNT-6 Hotrod with a Helikon SL. An incredible combination. I can't imagine better sound without spending what a new car would cost.
Are you sure you didn't mean effective length? The Triplanar has an effective mass of 11 grams and the VPI 12.5 an effective mass of 11.2 grams. Not much of a difference. The VPI 12.6 has an effective mass of 10.1 grams. Also, not that different from the Triplanar.
Now if you are talking effective length, the Triplanar is 250mm and the 12.5 and 12.6 are 315mm - a significant difference.
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