The algorithm for placing struts sounds quite simple.  Chimera has ribbon splines that go exactly through the C-alphas, and can also join side chains to a ribbon even when the C-alpha is not on the ribbon.  So I think that won't be a problem.  The Jmol strut code I looked at looked more complex than what you describe.  If it simply chose short distance struts wouldn't you get a bunch of unneeded struts say within one alpha helix, and maybe lack some long range struts that are needed to hold everything together?