forget about pace, watch, etc. This is about your battle against the mountain, and she usually wins :-) Figure out what angle works for you that you can still run, but you WILL be walking A LOT. 15 to 30 mins added to your marathon time is a good guestimation for your uphill time, but the downhill is the hard part. I always think it's more of a dance coming down simply because of the focus required and quick feet needed to handle the rocks, drops, and roots. Be careful from miles 17-22 as your focus wanes a bit where the downhill is a bit more gentle, and the smallest of rocks will jumps up and grab your feet..... :-) With the steepness of the last 3-4 miles it becomes an exercise in braking, and your quads will be protesting. Have fun though because in the end it will be EPIC. Oh, and I am much less sore from Pikes than from your regular ol' road marathon.