Great! Glad you got the beast tamed. Have fun!
Apparently I did not have libsoqt4-dev installed (what I get for
staying up late & trying to figure things out while too tired).
With that package installed, FreeCAD 0.13 rev 1160 compiled
successfully and radii are now happily tangent to one another.
With apologies for not reading the CompileOnUnix page more
thoroughly & thanks for the help,