Thanks for all the input!
I'll climb around this week and see what is possible. Unfortunately the existing vent through the roof is about 10 feet from the offending sinks with no reasonable way to access it. The under-counter vent is located high within the sink cabinet and has room to easily add a "T" fitting that would not be prone to allowing water access from the tank.
It's interesting that the shower does not emit any odors, only the kitchen sinks? The shower seems to drain into the common drain/vent pipe that goes through the roof. The Plumbing Schematic available from Winnebago, although helpful, is not the same as for my installation?
I use the GEO system in both tanks and am not a fan of using other treatments to cover (or eliminate) the smell. The issue seems to be pressure build-up through adding water to the tank, or sloshing within the tank while driving (most frequently) and overwhelming the "P" trap.
Thanks again.