7246VXR and Downstream DCC

First off, I'm a journeyman CMTS handler. I've kept my system alive and functional, but I've reached my limit of understanding when load-balancing via the CMTS itself is required.

This is the scenario I'm having problems with. Our system is comprised of a single 7246VXR, fully populated with MC28U/X linecards, and wired in what Cisco refers to as "sparse mode". Single return fiber nodes are wired to single ports on the CMTS, there is no sharing but for two oversubscribed nodes returning on two upstream frequencies per fiber ("frequency stacked" per the Cisco lingo). All downstream frequencies can be seen by the modems plant-wide, so the average modem will see 8 downstream frequencies when initial ranging, but can only return on a specific port.

What I need to do at this time is load-balance the downstream usage, preferably without rewiring to "dense mode" due to bandwidth issues in the upstream. We have severe noise issues that limit DOCSIS upstreams to the 30-42mhz region.

In reading the Cisco document, I think what can be done in my situation is to create 4 load-balance groups, comprised of downstream frequency pairs on the same linecard, example being Cable 3/0 and 3/1, to allow DOCSIS 1.1 and 2.0 capable modems to shift downstream without rebooting (as they would have to if they shifted across linecards, ie "DCC initialization technique 0"). Can this be done on a "sparse mode" plant, since the entire Cisco reference seems based on "dense mode" wiring?

Thanks in advance for your input.

Tim