We've just been facing this problem ourselves. One reason to set the serial number in the main sequence is if the serial number is read electronically from the UUT. It was assigned at a previous test station.
We tried setting UUT.SerialNumber, and it mostly works fine. The correct serial number appears in the report, but the report file name (which we do "per UUT") is incorrect. That's because "Determine Report File Path" runs before the main-sequence call.
I think ideally, "Determine Report File Path" should be split in two. Run it before the main-sequence call if you're not configured for one report per UUT, do it after the call if it is configured for one report per UUT. That way, everybody wins, as far as I can tell (but I'm still new to the
TestStand game).
- Ron