-더라도 means "even if, even though, supposing that" 했더라도 is used for emphasizing hat the event was finished -더라 used for just delivering new experienced fact to listener. 했더라 is used for emphasizing that the event was finished ex) 인천 영종도 공항신도시에서 영화촬영을 하더라.(I'm not sure the event is finished or not) 나 빼놓고 다 출근했더라.(I'm sure the event was finished)

하더라도 --- Even though sb do(will do) sth, 했더라도 --- Even though sb did(have done) sth, For me, very difficult to explain belows in English. 하더라 했더라

Not a native speaker (nor an expert), but I've studied the 하더라/했더라 issue enough that I should be able to explain it. ㅎㅎ The "더" communicates the nuance that you've experienced this thing personally (or learned about it). It's not something that everybody knows or that you have known for a long time. It apparently sounds very strange to use past tense + 더라 with an adjective (descriptive verb, whatever you want to call it). "해운대해변에 가보니까 좋았더라!" X "--- 좋더라!" O You're expressing a snapshot of your experience, so it makes sense (to native speakers at least!) to use present tense. I've found it hard to wrap my head around this issue, so I thought it might be helpful to share my conclusions with a fellow learner. 희섭 씨 covered the rest perfectly.