When running a Milestone report, I'd like to pull the participant's t-shirt size which was collected in the additional questions during registration. But that field is not an option when running the Milestone report. Conversely "Date Milestone Achieved" is not a field option on the registration reports. 

My work-around for this is to update a constituent field with the shirt size during registration and then pull that in during the Milestone report. This is a little clunky and also adds a constituent field that may not get updated at any other time.