I'm far from an expert but there are specific slots reserved for ranging and its seems unlikely to me that you would get T3 timeouts due to one user doing large downloads. The normal explanation I have heard for T3 time outs is Noise, normally on the upstream.
This is the Cisco page that explains error messages
»www.cisco.com/univercd/cc/td/doc ··· errs.htm
This explains ranging slots
»web.archive.org/web/200712180625 ··· l/09.htm--
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