I'm assuming that if Bend is off, Weld doesn't apply. I found that if one part is parent of another, and one has bend off and one has bend on, on the part which is bend off, its vertexes at the join go halfway to the matching points on the non-bending part. LIkeliest Poser does all the Weld calculations for all parts; but then for non-bend parts it does not use the resulting values to move the edge points.