Seren's right Every downhill has 2 90 degree corner at the bottom.... So you have to slow right down, then climb up the next hill from virtually zero. I did IMRegensburg in the rain in 5:30 I did IMWales bike in 6:30 I did IMLanza bike in 6:00 Hope that puts it into perspective....
I don't find those gel seat covers work that well. What is the problem? If it is just sore sit bones then they will toughen up. If it is delicate bits rubbing then maybe a saddle with a gap in the middle will help more. Finding the right saddle is a bit of trial and error (and can be quite expensive) some shops do try…