If you have used Scaling or Morphforms as part of V4's settings, be sure to conform with Scaling included.

The other most likely causes are that either the clothing doesn't have matching morphs for all those you used on V4 (select V4 body, Ctrl-C to copy settings, select clothing body, Ctrl-V to paste setting) and/or you haven't "magnetised" the clothing (to match JCMs).