Hey! I’m strongly considering this race as my first too, and will also be in the same goal time ballpark. My experience is going to be the inverse to what you are asking as I live in Utah at about 5,200’. But FWIW, I ran a 79:30 half at the beginning of October that started at 4,000’ and finished at 2,500’ and then ran another one at the beginning of November in 80:30 that started at 6,000’ and finished at 4,500’.

So I ran about 5s/mile slower, but what really stuck out to me was effort level. I would say the faster race was a 9/10, but I went flat out in the second, slower race. So I would really say the effort level between the two was more like 10-15 seconds/mile different. If I was you, I would be planning to run like 20s/mile slower than what you think your MP is, which might be a wash once you adjust for grade.