Fixed! Instead of slider, used half the Distance between start and end points. Different curve than the piped BiArc but consistent for all three sets of circles.
TangentCrvs_2022Feb8c.gh (37.5 KB)
P.S. Extended bottom range of ‘Bend’ slider (changed from min = 0 to min = -1, blue group) to get concave tangents in addition to convex,
TangentCrvs_2022Feb8cc.gh (33.3 KB)