After an otherwise successful run, I'm getting a warning when 'use only custom dir' is selected and pointing to a 7z pkg with both options checked.
"DPs Mass Storage Drivers MSST script could not find result of MSSTmake.exe"
'Use only custom dir' only for use Folder (with subfolders) with Drivers like unpacked DPs.
In your case select 'Use Package' option in ScrollBox select
'Use Custom Package' and set point to a (7z or bin.script) pkg in 'Custom Package >' FileBox
PS: I cannot understand as you could specify a way to file when use 'use only custom dir'