Hi Timothy -
I'm able to pull a custom field from a form at the Portfolio details using this code:
displayname=Portfolio - Product Group
linkedname=project
namekey=view.relatedcolumn
namekeyargkey.0=project
namekeyargkey.1=portfolio
namekeyargkey.2=DE:GCP Product Group
querysort=project:portfolio:DE:GCP Product Group
textmode=true
valuefield=project:portfolio:DE:GCP Product Group
valueformat=HTML
Hope this helps,
Teale