I'm trying to make a base for a tube feature that I have.  The issue I'm having is that the tube feature is not planar (some of the tubes are below other tubes).  I'm unclear on how to make a boss to support the whole structure that doesn't close up any of the tubes... thoughts?  I can't just use an "up to next" boss, because the feature doesn't terminate the whole boss...

these are the tubes.

a cross-section.  you can see that some are below others.