Blocking with Duplicate Stitch

I am working on a sweater for my grandson and need to do some duplicate stitching on the front.
My question is do I block the piece before or after the stitching? I’ve not done duplicate stitch before so wasn’t sure which was the best sequence for the stitching.
Thanks for your help.

Are you using the same type of yarn for the duplicate stitch (wool, acrylic?)? My tendency would be to do the duplicate stitch and then block but I’ve only done small areas of duplicate stitch.