You need to edit the slot 501 and 502
;upper arms on chassis
slot -0.5009 0.0401 -1.1427 0.000 0.000 0.000 501 < THIS IS FL
slot 0.5009 0.0401 -1.1427 0.000 0.000 0.000 502 < THIS IS FR
slot -0.5476 0.058 1.1797 0.000 0.000 0.000 503
slot 0.5476 0.058 1.1797 0.000 0.000 0.000 504
coordinates are respectively L/R U/D F/B