Figure out what your acceptable DOF is, with a DOF calculator. Here's one of many:
http://www.dofmaster.com/dofjs.html
They make phone/tablet apps for this, too.
Maybe you need something to pull focus with, too. There are several cheap solutions on ebay & similar sites. Also expensive ones, I guess.
However, without knowing what your actual shot is, I dunno how specific an answer you can get to your problem. Sounds like you need more hands-on experimentation to me, though, with regards to how DoF actually works.
You were able to counter-balance that lens okay on a Glidecam 1000? It's heavy!
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