DarkestRose, the way to do this in P4 or PPP is to use the morph dials, trans dials, along with magnets on the outfit to get it to fit the figure - just do not conform it to the figure, since the jp settings will probably be wrong. Also, make sure you zero the base figure first before you start. To do this, turn IK off for SP3, select the body, open the Joint editor, and click zero figure. You also want to set x, y, z tran dials in the hips and feet to 0. Once you have the clothing scaled so that it lines up and fits around the figure like you want. Delete the base figure - not the clothing item. Then export the clothing item as an object, uncheck all boxes. Now take the blank SP3 cr2 as described above, and put the object in the geometry folder where you want it, and point the target path in the Cr2 to call it up when loaded. There are two lines to change in the Cr2, and would look something like:

figureResFile :Runtime:Geometries:nameoffolder:nameof.obj

The body groups should match okay, since V2 or V3 clothing, is grouped the same as SP3. Converting P4 clothing, might require using the grouping tool on the object to resection the body groups. More involved. I would avoid using the Setup Room in PPP, since this seems to do weird things at times.