Doubling up servo's...

Curious.. has anyone ever doubled up or stacked servo's. I was planning
on using two on a common drive timing belt [one belt, two servo's and a
pulley which they both drive]. Only one of the two would have a encoder
and the power leads from both of them would be wired to the same
drive.. [I'm not sure if they should be parralleled or series..]

Curious...

Jarrett Johnson