Before trying the nth-child approach, which is wrought with browser support issues. I thought I'd try using keyword modifiers to alter the class on listed items before installing selectivizr.
Ideally, if I could have on the default format something along the lines of:
<div class=" %asset_position^modulo:3^eq:1:col-md-3% %asset_position^modulo:3^eq:2:col-md-6% %asset_position^modulo:3^eq:0:col-md-3% "> <!-- LISTING CONTENTS HERE --> </div>
It seems that the modifier works for other number keywords (I tested asset_assetid) but not for asset_position. I also tested if asset_position works on other number modifiers and it doesn't. Does anyone know why? Is this a bug?