I think that some used with the grooved belts may have a slight
increase in the dianeter at the middle to keep the belt centered.
This wouldn't work too well on a traditional "V" blt, methinks.

Walls may be needed to hold the belt in place, even if well-aligned. It
might work, but watch out for unusually wear

I think that it might need a bit of thought.

Karl (Hate to wrap a belt around a fan) Haas

Have you already started or are you just looking at designs. It think
there are several ways to do it without needing that type of pulley, but
you may have  something that requires a unique setup . Tell us what you
have and someone here may already have done one like yours.

For "back-riding" pulleys, I like to use modern timing belt tensioners.
Most have a bracket or mount that you can adapt. I am using a Subaru
belt tensioner on Linda's Hawk's AC.

You may also look at:
http://www.ncsdc.com/TechnicalPages/AC/studeac.htm

Ray