Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Isoparm Subdivision
SWEEPOBJECT_ISOPARMParameter: End Scale
SWEEPOBJECT_SCALEParameter: End Rotation
SWEEPOBJECT_ROTATEParameter: Start Growth
SWEEPOBJECT_STARTGROWTHParameter: End Growth
SWEEPOBJECT_GROWTHParameter: Parallel Movement
SWEEPOBJECT_PARALLELParameter: Constant Cross Section
SWEEPOBJECT_CONSTANTParameter: Banking
SWEEPOBJECT_BANKINGParameter: Keep Segments
SWEEPOBJECT_KEEPSEGMENTSParameter: Use Rail Direction
SWEEPOBJECT_RAILDIRECTIONParameter: 2-Rail
SWEEPOBJECT_BIRAILParameter: Use Rail Scale
SWEEPOBJECT_RAILSCALEParameter: Reverse Normals
SWEEPOBJECT_FLIPNORMALSParameter: Stick UVs
SWEEPOBJECT_GROWUVParameter: Scale
SWEEPOBJECT_SPLINESCALEParameter: Rotation
SWEEPOBJECT_SPLINEROTATIONParameter: Rotation from
SWEEPOBJECT_ROTATIONFROMParameter: Rotation to
SWEEPOBJECT_ROTATIONTO